First, stop looking her up on Facebook. Block her if you have two.

Second, there's nothing your BF is going to be able to say or do to make you feel secure IF the reason for your insecurity is your own lack of self-esteem and feelings of self-worth. These feelings you have are yours to handle. I'd highly suggest speaking to a counselor about your insecurity and working through it with them.

I do understand the feelings. When I started dating DH, I was coming out of an abusive/toxic marriage. I had ZERO self-esteem, and I was convinced that my DH would go back to BM if given the chance. I had no actual reason to believe that (BM is the hottest of hot messes), but my own lack of self-esteem made it hard for me to actually believe my DH would want me. It has taken literal years of working on myself to get to a place where I'm mostly comfortable with who I am.

BUT, I've had to work at it. My DH helps a lot by listening to me, putting in boundaries with BM, and over time becoming more and more apathetic to her. It has definitely gotten easier as the boys get older because DH has less and less to talk to her about, and there are fewer and fewer "family" activities that they "have to" do together (e.g. mom and dad pictures/ceremonies for Boy Scouts). DH has also gotten sick of her presence and wants to spend as little time with her as humanly possible.

So, get into some therapy. Read around here about appropriate boundaries. And for the love of god, meet his kids and see how he parents before going any further in this relationship. BM has zero right to dictate who your BF introduces the kids to. If it's time to meet them, then you should meet them. BM is going to have to realize that she doesn't have control over her ex anymore, and your BF has to realize that his balls are back in his pants and out of his ex's purse.

Lastly, stop asking him to share his communication with BM with you. You either trust him or you don't. If you don't, this won't last. If you have reason to think his interactions with BM are odd, post them here and we can help evaluate.

Your partner's ex has absolutely no right to have any say at all in whether you meet his kids or not.  You need to do that asap, in order to find out whether you can stomach the dynamic between them, whether he is a good and firm father etc.  With the way he behaves with his ex, I suspect he won't be.  You only need to read around this site to see how much stress, anguish and mental ill health is caused by ineffective bio parenting.  

The thing about your feelings about their relationship, needs to be explored in therapy, as it is mostly your issue.  

If you live with your partner, how do the kids have no idea you exist? Do you hide when they visit, or leave the home? It seems like this might have some bearing on your insecure feelings - your DH is cares more about what BM thinks than about whatever you are having to do so his kids don't know you exist.

In any case, try some individual therapy for yourself and quit stalking her on facebook.

How is this a seperate issue?: "At their mothers request, I don’t have a relationship with the kids and they have no idea I exist."  You feel like sloppy seconds because that is how you are being treated.  You are being treated like a piece on the side that has to be hidden.

By the way, it is not recommended that a bio-less partner hooks up with another partner who has children from a previous relationship.  Why?  Because partnerships are supposed to be give and take on BOTH sides.  Too often what happens is the partner with children basically gets to do whatever they want under the guise of "it's for the kids' sake," while the bioless partner is expected to suck it up and take it, time and time again.  That is not a partnership; it winds up being more like a, well. . ., as you feel and suspect, a situation where the bioless partner feels like sloppy seconds, while the partner with children gets to have their cake and eat it too, and gets to basically have two spouses.  Usually the ex- winds up being spouse #1.  Oh, they may not be having sex, but the veil of the relationship is still there.

And, I'm saying this as a bioless SM who married a man with children.  You are young and naive and for some reason have been already led to believe it is YOU, when it is more than likely the no-win situation your partner is already placing you in.  It won't improve.  Leave, and find yourself a man who is your true partner and knows your true worth.  Also, he may be keeping you a secret because he is still trying to work it out with bio-mom, while keeping you on the side "just in case."  Not worth it and not worth the mind games.

Your BF. Doing that she is controlling your life with your BF.  You have to understand that you are not going to have the same life that the ex had with your BF. They did not have kids at first so it was all the ex. You have to share BF with his kids. 
You also will be jealous, of BFcand his ex life. She had a wedding first, most likely a big one.  You most likely will not. People don't like going to second weddings,  she has the big engagement party, wedding dress, honeymoon.,  she had the kids first. He been through it two times already.

You will feel he is gaslight you, when he saids things like your wedding is special, you having kids is special. 
 

If you do not work these things out now it's going to follow you throughout your relationship.

You feel insecure because your SO is allowing BM to control his life and decide what part you play in it. If this guy can't stand up to his ex, he's not partner material. Don't give him too much longer to set some boundaries on her. 
 

I have no kids and DH has one. I don't think it's such a terrible arrangement, but it depends on what kind of parent he is.  I didn't help with his son or feel that DH centered everything around SS to my detriment, and that's why I'm still here. 
 

Focus less on whether you are good enough for him, and more on whether he's right for you. You have to meet his kids and see what kind of parent he is before you can decide that. As for BM, be civil if you meet her by chance, but keep your boundaries strong. You don't have to have any sort of relationship with her. I've said about 10 words to BM in 10 years. 

Have you ever heard BM say anything about the kids not meeting or is all of this coming from your BF?  

If you haven't heard the conversation first hand, then I say your BF is full of shit and he's still sleeping with his baby momma.

I would be very cautious with this situation.  a year is more than enough time before he introduces you to his kids.  you are living together arent you ?  how does he see his kids when you live together, do you have to leave the house for the weekend and stay hidden?  I wouldnt really obsess over the ex that much and stop looking at social media,, i would me more concerned that he may be more intertwined with the ex still than you think.do they own assests together still or is he completely detached and free to move forward with his own life?  If he hasnt introduced you to his kids because he is worried about how bitter the ex will be ,, he is essentially choosing to care about her feelings over yours.  My DH wouldnt pull into the exes driveway when i was in the car ,, instead he would park on the street and walk in to collect his kids because she was so bitter and would crack the shits everytime if she saw me in the car,,, well that used to make me feel like crap that he was ok to accomodate her feelings of bitterness over my feelings of hurt that he hid me in the car so she wouldnt see me,,, instead of being a man and pulling in the driveway not caring how it makes her feel!  think about this carfeully and maybe disscuss that with your BF.  Dont be shy to ask him if they still are connected with assests also ,, this is a tie that you will want to be very careful with ,,,, if he does ,, he needs to be efficient in seperating and finalizing everything ,, as this can drag on month after month then into years.  TRUST ME I know!    I was a year in when i  found out they still had joint property and bank accounts,, it took close to 5 years for them to finally seperate assests and close accounts etc becasue the ex was so bitter and sabotaged every attempt made to finalize everything until finally the court stepped in and ordered her to do so.  But during this whole time ,, my relationship with SO couldnt ever move forward fully as we couldnt get our own joint bank accounts or buy a house together or anything whilst they had joint assest as she can then claim access to any funds i contribute with my BF.   There is no doubt about the fact that the BM will always try to intervene and have some form of control over your BF,,, its your BF who needs to reclaim his testicles , be a man , clean up his mess and createfirm boundries with this women.   I spent 8 years doing it but gave up a couple of weeks ago and told him to move out,, even with the BM remarried and a new baby ,,,, the mess never ends.  Good luck and PLEASE stay firm on your boundires with your BF regardless, dont tippy toe round any situation and dont be frightend to speak up and trust your gut!

OP, if you haven't run yet, please listen to the advice that sounds hurtful and untrue, because for a lot on this site, those hurtful scenarios are *exactly* what happens.

And I know you want to deal with the insecurity in a bubble, but you can't. This isn't just you causing it. Your BF is doing things (or not doing them, more accurately) that are leaving you feeling shaky. Not standing up to BM and letting her rule everything will make anyone feel unstable. TRUST ME: been there, done that.

Your BF being abused is very unfortunate, but many of us on here have been abused, as have our spouses. It may be a *reason* why we've done or dealt with crappy things, but being a reason doesn't *excuse* it. If your BF can't stand up to BM due to abuse, then he needs to seek counseling and actively look into how to deal with an abusive ex who is also the other parent to shared children. There are lots of tips to help minimize ongoing trauma. And he has to fix those issues in himself BEFORE he can commit to another person fully.

Ultimately, if it's your BF's actions that are leaving you feel shaky in this relationship, then it's your BF who has to make changes. He can't let BM run his life, because THAT instability will bleed over and be felt like you. It also puts you in a prime position to be a victim of gaslighting, even if unintentional. You'll feel like something is way off, and when you try to address it, it'll be shined back on you.

If you have abysmal self-esteem, fix that. But know that fixing that aspect of yourself won't cure the insecurity if the root cause is your BF and his actions. It sounds like, as you post more and vehemently want to only focus on this one aspect of your relationship, that your BF is the cause of a lot of your stress and anxiety (and you likely know it, too, and don't want to be smacked full in the face with it; been there, done that, too).

None of this means your relationship isn't salvageable, but some serious changes need to happen fast for it to become healthy and productive. First being your BF making decisions about his own kids and getting help to deal with his own issues related to BM. That includes him finding the biodad version of StepTalk and asking boatloads of questions and doing his own research. If you have figured out you need the help, and found a place with advice, he can find the same.

We don't polish up the truth here. Other stepparenting sites do because most are dealing less with crazy exes and more with just annoying ones. Here, you'll find most of us are dealing with exes who are abusive or downright crazy (sometimes bother), parental alienators, consistently jobless, amoral at best, etc. None of this is new territory for us, and we come from a place of protecting folks from going through what we've gone through.

So, take to heart what we say and do some actual soul searching. It's not fun to have a bright light shined on something ugly, but it's the only way things improve. 

Im 5.5 years in. I met my DH when he had JUST gotten separated. They were still firmly enmeshed. SHE did not want to meet me, thusly the children did not meet me, for exactly 2 months, and this was because she had a new bf that she introduced them to, so he insisted that it would happen. 

They are much less enmeshed and now its because of child support, and shes a toxic troll. HE had to create and enforce boundaries, and when I howled enough he stepped up.

AS you have mentioned you will post the reason that you havent met the kids in another post, I shall reserve judgement until then.

GET THEE TO THERAPY. That is my rec for dealing with insecurities. I let mine eat me up and torture me. So not worth the time and energy. Spend that time and energy on YOU.

There is nothing to work out. Your SO can introduce his kids to whoever he wants to introduce them to on his time. BM can F-off.

However, I would caution you strongly about going forward with a relationship with a guy who is so enmeshed with his X that he allows her to dictate how he spends his life and his time with his kids as well as gets all worked up over the death of his X's father.

I couldn't care less if either or both of my XILs died.  While I was reasonbly close to them when I was married to their daughter they are the people who created and raised that adulterous cavern crotched skank whore and ultimately were Federal felons who ripped off $Millions from my XMIL's employer.

Save yourself from this tragic slow motion train wreck of a failed man, father and husband (or near husband).