Help !!!

Hello women who were in abusive relationships. Please tell me how you got out of it. I have an abusive husband and he threatens me about our son and tells me he will take him away from me. He also tells me he will make my life a hell if I try to take the son away from him but I won't!!! He also told me if I find someone he will not allow that person to watch my child. I don't know what to do. I don't know where and who to go to. He is a sick man!! But I don't want to take the son from him because he needs the both of us. Please give me advice because I am at a point in my life where I am scared to leave and need help getting myself out of this relationship. He constantly criticizes me and if something doesn't go way he wants it to I am a terrible wife or mother. It's almost an everyday thing. I don't know how much I can handle it!!