I can only hope that you have some family who will help you out of this situation and soon. You don't deserve to be treated like this and having sex with him after, I'm not sure what kind of message that is sending...this may get really ugly, and your child doesn't need to see this. Please please please get away as soon as you can.
My first husband hit me once, that was enough, and I was gone but I had no children at the time. I know disrupting everything doesn't feel like a good idea, but really IT IS! Is there a shelter you can go to? Or change the locks and get him to pay support? Big hug and prayer for you.