Ugh so sorry you are going through this and at 9 months pregnant. How awful.

But honey, you have a DH problem. He isn't ensuring skids are doing as they are told. He isn't ensuing your boundaries are in place such as skid leaving for BM's or getting dumped on you. And he isn't helping you with the tasks you ask of him.

Skids could act like angels. BM could channel mother Teresa but until your DH steps up it will always be this way. 

Before checking out, make a list of the things you want to discuss. The things that are not working. Then sit down with your DH and work out a plan. One that he MUST stick too. Or ultimately you checking out with be for good. 

I'm sorry you are dealing with this nonsense, but glad you are at a point to take care of you. No is an acceptable answer, especially in step-life. Time to put some of this on your DH. I agree with dysfunctionallyblended- make a list of what needs to change. Skids need to do chores, clean up after themselves (including pee- I do not clean pee off a toilet. If I see it, I tell my SO, who in turn makes SS clean it up), do their laundry....your DH should be ashamed of himself for expecting you to do all of this at 9 months pregnant instead of having skids help.

Please stay checked out until things change, and if they don't, do what you need to do. Your health and happiness matters too.

Your husband is definitely the main problem. He has no respect for you. Definitely do what Dsyfunctionally and Step-girlfriend suggested.

When the skids showed up after school, how did they know you were home?? Was the door unlocked or do they have a key?Please stop allowing yourself to be a skid-sitter and set boundaries for yourself.

He should not be working 7 days a week and dumping  those kids on you.  Your SK don’t want to spend time with you, they have two parents, Ther really don’t need a third. If your DH can not be home, then those kids should be with BM.  You are not a free Babysitter.  The faster to tell DH the better it will be.  If he is not home why is he depriving BM of her kids ? 

Please put yourself and your health first! If you don't, your toddler and unborn child will suffer, too. Forget about the skids. Not your problem. Have a come to Jesus meeting with your husband and overhaul the way you do things. Please. 

Has anyone just stopped juggling and let the balls drop? Did it work? 

Stop doing EVERYTHING that you are doing for H and the stepkids and see how fast you'll get their attention. Sometimes sh!t has to hit the fan before anyone realizes just how much you were taken for granted. Place yourself and the health of your toddler and unborn baby 1st. All this extra stuff you're doing and the lack of respect and consideration that you're not getting is insane. Your H has to step it up and if he's not home his kids shouldn't be either. He's going to have to learn the hard way that you're not a doormat. And yes it works.....do it and you'll see.

All of this is so, so wrong. 

You are 9 months pregnant and being treated like a slave. 

NOT OKAY. 

My DH knew better when I was pregnant. He helped a lot at the beginning, but man, during the third trimester, he just KNEW. Not one dish was found in the sink the entire third trimester. He made sure to clean up after himself and his daughter as SOON as a mess was made. I was in full-blown nesting mode but also incredibly exhausted so he made sure I had nothing to get emotional and upset over. 

Your husband is being inconsiderate. What on earth is he teaching his children? They are going to be complete jerks one day when they have heavily pregnant wives! He should be teaching them to cook, clean up, etc. for YOU right now if he wants them to be half decent men one day. 

Disgusting. I can't imagine being treated this way while heavily pregnant. 

Girl I am tempted to move IN to BM's neighborhood just for these reasons. You are about to pop and have a toddler on your hands with a DH that is barely available. Embrace the fact they are at their moms. If they are there then they aren't at your house making a mess, dirtying dishes, peeing on the seat and raiding your pantry. Dh not home and Skids don't want to listen? Send them to their moms. DH not home and skids don't want to eat what your about to fix for dinner? Send them to their mom's and cook just enough for the three of y'all. They aren't playing with the outdoor toys? Girl either sell them or cover them so your toddler can grown into them and they'll still be in prime condition! The skids just sitting around the house on their phones? Change the wifi password and play dumb so they either run up BM's data or go back to her house for wifi. Win:Win either way. Encourage your DH to get a passcode door lock so you don't have to fumble with keys and don't tell the skids the passcode to get in. Tell your Dh it is because they forget to lock the door and you don't want the toddler going out (it auto locks after a few seconds) Great baby feature! Side perk is the kids won't be able to barge in anymore. If you have a garage have your DH clean it out so you can park inside and hide your vehicle so skids won't know when you're home. When they comes knocking DON'T ANSWER. They can go back to their moms until their dad gets home. You can say you were napping or didn't have your phone on you when they tried to come over. Instead of thinking of how caged in you are with BM right up the road and the kids way of just coming and going...think of all the ways you can force BM to babysit her own children while you prepare for another baby. 

Your DH should not have 50/50 custody if he is working 7 days a week and can't contribute to the care of his children.  I've done the whole, "I'm on Strike!" bit and it only backfired on me leaving the house in utter chaos. What did work for me was minimalizing everything and cleaning out the clutter.  Another thing that worked was hiring out household chores/projects that DH was "too busy" to do. Once there was another man taking care of his business DH stepped up! 

I'd suggest hiring a sitter to help w/skids while you are in the last part of your pregnancy and after having the baby. If DH claims it's too expensive then perhaps the boys can stay with their mother instead.  DH could also adjust the times he has the kids and still have 50/50.  Is there a grandma that can pitch in and spend time with the boys during DH's parenting time?  

The key for you is to stop being so available. The problem with being a SAHM is that EVERYONE thinks you're home eating bon bons and watchings soaps so of course you don't mind watching their kids.  Only you know how to remedy this, I'm sure you can brainstorm some ideas.  Just the other day at work a delivery driver came and dropped off groceries.  She was a momma and had a toddler in the backseat while she did her deliveries.  

The issue is that BM and DH want you to provide free unlimited childcare for them.  Your task is tactfully handing their parenting duties back to them.