Staying with husband for son

I want to leave him so bad I am not happy and when he gets mad he goes crazy. He screams at me pushes me and throws stuff, makes holes on the wall. Today he pushed me (I’m 10weeks pregnant, left a scratch on me, and Broke our closet mirror sliding door. I am terrified of leaving him because I don’t want him to get Custody on our two year old son. He doesn’t know how to take care of him, drinks a lot, and the way his anger is i am scared to leave him by himself with my son. He does try hitting him and yells at him I cant imagine if he’s alone. Please help on what to do.