MamaDuck, hang in there. You are responsible for two lives now--yours and the little one you're carrying. That's a lot of responsibility, but having a mother's love in your heart can make you stronger than you ever knew. It sounds like you aren't committed to leaving, so I won't give you advice on that front. I will only say that I recommend you take a look at lots of other threads of people who are married to alcoholics and addicts of all kinds to get a look at what your future might be. Maybe if you're uncertain, you should at least postpone the wedding. Getting out of a live-in relationship can be legally easier than getting a divorce.
Be strong and take care of yourself. Meanwhile, keep coming back here. I have found this to be an endless well of kindness and support.
Best wishes to you, and God bless us all.