What do I do?!😭

So I'm trying to leave my SO and he's making it impossible. He takes any extra money i have so I can't save. He's forcing me to raise his children from a previous relationship. He refuses to get a job. I have a fulltime job and I'm 10 weeks pregnant. Every time i try to leave he tells me he'll take the baby and I'll only have weekends. He's abusive towards his son, but says I'm a bad mom when all I do is talk to the kids about their behavior. He controls every aspect of life. I can't go anywhere or do anything unless he says it's ok. I can't even go to my own mothers house without getting yelled at for hours. I'm just so lost and don't know what to do. I'm only 17 and I won't be 18 until December (2 months before the baby is due). I've seen a lot of posts where women got a lot of support. All I'm asking for is some advice not pity. I've tried to find other places to go. The only place I can go is my dad's, but he lives in the middle of no where and I won't have a way to get to work so I wouldn't be able to support myself or the baby. Sorry this post is long, but I'm scared and need help