I desperately need help on how to deal with/get over my blended family life.

I met my SO 2 years ago through a mutual friend. At the time his son was 1 year and 3 months and I thought he was the cutest little thing. SS's mother and my SO were never in a relationship...it was a one night stand that resulted in a pregnancy. He asked if she was on birth control and she said yes, but she wasn't. He tried to get her to have an abortion but she refused so they moved in together so he could be with his child full-time. After about 9 months of them living together, he kicked her out because she is crazy (would hit him, threaten to call the police on him, talk to other guys behind his back, etc). He told me he never loved her and said that he never told her he did, but I have seen messages that he sent saying he in fact did (and this was about a month before we started dating...something thing I struggle with because I feel like he lied to me). So when SS's mother found out we were together, she messaged me calling me a homewrecker and derogatory names which made me feel really out of place. SO tried to reassure me that she was just jealous and mad that they were no longer together. Which I can understand to an extent...she lost her family but at the same time she had a child with somebody she wasn't in a relationship with.

In the beginning, our relationship was amazing. I felt so in love (first time ever) and I was walking on cloud 9. I had been battling an addiction and was recovering when we met and he kept me sober which is one of the reasons why I fell so hard for him...he was the only person who motivated me to be a better person and to stay clean. Everything was perfect. I moved in with him a month after we started dating (it was fast, I know) and that was because I could not stand the thought of being away from him. January 2017 (6 months after we started dating) we started to try to get pregnant (now that I'm looking back on all of this maybe I am the crazy one LOL). It took us 5 months to get pregnant and the whole time leading up to that I felt so discouraged and left out. He spent so much time with his son and I was so jealous. I didn't have that bond with SS and felt like an outcast all the time.

When I told SO that I was pregnant the first thing he said was "Oh great, your due so close to [SS's] birthday" because my due date is 2 weeks after his birthday. It made me feel like he was mad and wished I hadn't gotten pregnant. He will randomly tell me that it was all my idea to get pregnant and will say it in front of other people which makes me feel like he's putting me down for it and embarrasses me, like I'm just another girl who trapped him into having a kid yet when we were trying he would get excited about it. He even told me one time when he was drunk that SS was a mistake and he's excited to have a child with me because it will be a child of love...so I feel like he gave mixed signals.

I am now 29 weeks pregnant and we are engaged and the past few months have been horrible. SS has entered the terrible twos/threes and is an absolute headache. He refuses to listen, hits, bites, and throws wicked temper tantrums if we don't let him do what he wants. He has gotten sent home from daycare multiple times because the workers cannot control him. We have him 50/50 so week on, week off. I dread the weeks that we have him and literally count down the days/hours until it's his bedtime or until he goes back to his mothers. I try so hard to love him like I would my own but I just can't. SO has picked up on my dislike for SS and it causes fights between us. He says SS will grow up hating me because I will treat him differently than my own son and deep down I know that's true.

Every time his mother comes to drop him off/pick him up I can feel my blood pressure rise. I despise her so much even though other than being rude in the beginning, she has never really done anything else to me. She even congratulated me on being pregnant and talks to SS about having a little brother and how fun it's going to be. She seems so okay with all of this but then again she is probably faking it. My SIL always hangs out with her and takes her newborn baby over to her house all the time to visit and I get jealous. I feel so childish! I hate the fact that my SO has a child with another woman even though it happened before we even met. I want to be the reason for his happiness. I hate that he has to talk to her and sometimes she will text/call him to talk about stuff that doesn't have anything to do with SS which makes me mad and it will turn into a fight.

All I've ever wanted was a normal family (I mean, who doesn't??). Mom, dad, children. None of this blended family stuff. I've even contemplated leaving him because lately we fight over EVERYTHING. He wants to take SS out of daycare when I have the baby to save money but I'm not sure I can handle it for one, and two I just don't want to deal with him. We got into a massive fight about it the other day and he said that he's not going to "punish" SS because I want bonding time with my own kid and looking after a newborn and (very hard to handle) toddler should be a piece of cake in his eyes. He was giving me such a hard time and his SIL even sided with me. I plan on going back to work and pulling him out of daycare risks losing his spot but SO doesn't care about all that. He's so worried that SS will feel left out when baby comes - all older siblings do, doesn't matter if they're full or half because newborns just need way more attention. I'm scared I'm going to get postpartum and just despise SS even more. He only sleeps 8 hrs max a night and refuses to nap. How am I going to function with little to no sleep and still try to find energy to play with him, keep baby happy AND keep my sanity?

I need help. I never expected things to be this hard for me. I know there's parts of me that's being immature and selfish, but how do I curb those feelings? How do I convince myself to just accept things and tell myself that I CAN do it all. I can be supermom. I can love SS like I love my own. SO and I can go back to having a loving, happy relationship. Is this all just pregnancy hormones? I'm half terrified to have this baby for fear of how it may make things worse