Hi, I'm so sorry you find yourself here. Especially while pregnant when your hormones are raging.
How old is your bf? Gently, it sounds as though he is very immature and self-centered. It also seems he didn't feel he was in a committed relationship with you just a couple of months into your relationship.
He has a pregnant girlfriend and cheats on you with another woman who is pregnant?
Honestly, I think you get past the hurt by removing this man child from your life.
As soon as your daughter is born (check with an attorney to find out if you can file sooner), I'd file for child support.
He not only cheated on you, he put your child's life at risk, he drinks too much, he contacted his ex wife, cheated with a pregnant woman and was let go from his job? Why was he put on leave from his job.
It sounds as though you have very supportive parents, I would rely on them to help you move through this heartbreak. If you were my daughter, I'd advise you to run and never look back.
He has shown you repeatedly who he is, please believe him. So sorry!
Consider finding a good counselor for yourself to help you push through the hurt. You and your daughter deserve a stable man who is willing to be faithful.