Advice on How to be Supportive Towards Alcoholic Boyfriend

Long Post.

My So and I have been together for 7 years. We have a son that will be 2 in August and I'm 15 weeks pregnant with our second. We only see each other and stay with him on the weekends at his parents house. We text and sometimes talk on the phone throughout the week. I'm a stay at home mom and live with my grandparents.

So has a drinking problem and will drink until he blacks out. I've been around it so long that I can't tell he's been drinking until he gets to that point. When that happens he acts like a different person or like a monster and becomes more violent towards me and everyone around him. It seems that it gets worse every weekend and last time I felt like me and my son weren't safe and stayed the night in his parents room and we argued about how all I do is run away when we have issues like this. I go home or rely on others protection. He screamed and yelled, said a lot of horrible things and we argued. He kept grabbing my feet, pulled my hair, and tried to pull me off the bed by my ankles to get me to come into another room to talk to him away from his parents.

I tried talking to him about how I feel and that this drinking has to stop and he is determined that he can fix it himself. I told him that we can still see each other and hang out and everything and I want to be able to support him as best I can but I'm not sure if me and our son will be staying the night with him for a while because I didn't feel like we were safe.

I have tried texting like we always have throughout the day but he says that if I am not there to support him the way he needs me, won't help him through something like this then he'll learn that he doesn't need me and won't be here for me anymore. He says it like he'll find someone else to be with if I can't stay the nights and tough it out until he's over it.

Any advice about how to support him while keeping myself and my children from being put in those kinds of situations again would be greatly appreciated.