Unfortunately the only person who can decide what to do is you. One thing to look at though, is if he treats you badly, how is he going to be around the baby? Even if he treats the baby ok, but continues to abuse you will not be good for your child.
I was with a guy for 1 year who was emotionally abusive to me, and previously to his wife, his children were definitely affected by this. I was lucky, I got out and had a supportive family.
Do you have any friends or family you can talk to? Not necessarily to give advice, but just to act as a sounding board, sometimes thats all you need. If you're afraid of what they would say, tell them this first, let them know you're looking for support, not judgement. Alternatively look for community support, try your phone book, or check with your doctor.
Best of luck
Rachelle, NZ, son George 10.12.02, Ian 15.06.04