Help/advice desperately needed.

I've been in a relationship with my boyfriend for 2 1/2 years. We started off very rocky, got better and then things started to change. He never really spent time with me, always stood me up , never wanted to come to family function or would come when it's almost over, had a drinking problem, which is still current. Not so much a drinking problem but when he drinks he gets very mean and aggressive. He would ignore me the times that he was home. And I became Luke a roommate/friends with benefits type thing. I had a very close male friend of 9 years. I eventually ventured off while feeling neglected by him even though we lived together. The friend of 9 years gave comfort and there then was an emotional attachment to him. He was always there for me. Through surgeries, problems,etc. While my boyfriend would put me on the back burning. The boyfriend found out that I was texting this guy and put an end to it and told me that it was cheating.. so I stopped and blocked the friend of 9 years. Speeding up to recently, for the past 6 months things have been going well and we were talking about getting married soon and starting a family. We literally started trying for a family a month ago and 2 weeks later I found out that he cheated and has a potential baby on the way with a friend of the family. AND also has another kid that may be his, from before I met him. I was under the impression that he had no kids. For these 2 years that has already past us by. And a week later that news, I found out that I'm now 4 weeks pregnant. I am really stuck and don't know if we should work on things, or should it only be about the baby and move on.please advise. I would love to hear from an outside person. I'm devastated, depressed and unsure of how to handle this situation.