I had a boyfriend like that and I felt I didn't have any choices. You do!
Get somewhere safe away from him. Look up some phone numbers of crisis centers in your area. They should be able to lead you to a social worker who deals with this sort of thing. Don't believe him when he says he won't do it again and that he loves you. He'll try it again. Once they think it's okay, they have no reason to stop. Do something now before you're too pregnant to walk. Don't think that because it's his baby that you have to put up with this kind of crap.
Take care of the two of you,