You might want to think about counselling, talking things through with a therapist usually gives you some clarity .As well realize how toxic the two of you are together. It happens to the best of us, and I've been in similar shoes (though not the pregnancy)
Have you ever heard the saying "Why buy the cow when you're getting the milk for free", he's getting both, so why change if he doesn't have to..
Things have changed now, you have a baby on the way, and your priorities have to change. Men can come and go, but the child is with you.You don't want drama to affect a child, it messes them up. It sounds like you really are ready to get some help. If you have a family or GP that you know, see if you can get referred to a therapist.
Much luck and congrats on the baby!