You’re not doing anything to “make him” be like this. Apparently something unhinged your guy when he couldn’t have free access to sex while you were pregnant and recovering from birth. He can’t manage it that he has to share you with your child either.
What he is doing is abuse. He doesn’t take you seriously when you tell him to stop. He isn’t showing you love or respect. Tell him to leave and mean it. The situation is already getting worse. I’m very worried about you and the baby.
The two of you got together when you were only 15. Making a baby doesn’t make someone into an adult. It appears that you have grown up and he hasn’t.
Please look into whether there is a domestic violence program in your area. You need some practical help and some emotional support. If you can’t afford your flat on your own, I hope you have family members or friends who will take you and your baby in. You need to get away from your boyfriend — the sooner the better.
I wish you well.