Lost???

I don't know what to do, I am in a relationship I don't want to be in with my son's dad, he is constantly degrading me and belittling me to the point where I break down in tears and cry my eyes out and also to the point where I want to hit something or destroy something. He is always calling me retarded, stupid, lazy, a bitch and he is constantly putting me down in front of our child and if I disobey him he smacks me until I learn. He even threatened me with taking my son away and he has even threatened me with making me leave. He doesn't love our child all he does is put him down all the time and I can't stand to see my son upset. I need help