My relationship is being ruined by a dog!

My boyfriend has had his dog for almost four years. Weve been together a little over a year, having a baby due February 5th and I have a 3 year old daughter. His dog is a pitbull and has been extremely aggressive and violent towards people and other dogs. Hes attacked and hurt our roommates dog more times then I can count, has bite me 4 times (drew blood), has snapped at my daughter, attacked other dogs walking by, and bit one of his friends which had to go to the hospital. I told him to get rid of the dog but he refuses! I've been looking and applying for apartments lately because it's getting THAT bad and stressful. Any advice on how to handle this? It's causing extreme anxiety and stress on me. :(