Sarah I agree with Abbey. We often see the good no matter how small or large the %
My ex did a great job hiding the bad %from me. If you would have seen/ heard him, you would have thought he just 100% good. He told me he loved me every day, told me how beautiful I was all the time. He never went a day with out telling me how lucky he was for having me in his life.......but he NEVER showed me. I would beg him to stay home with me and as he spoke his beautiful words he would walk out the door. Find someone else and show her how much she meant to him.
There comes a time in our lives that we have to start taking care of ourselves and not worry so much about fixing theirs. I have seen first hand what drugs can do to the person you love, and how love for the good in that person compels us to hold on to them.
Only you know what you are to do. But may I suggest that you don't bring a child into the mix quite yet?. Ask your self this "Is he really father material?" Because no matter how much time goes by you can leave but if you have a child with him...that child will always be a part of him and that will keep him in your life.

Sarah,
You have to come the relization that you can not help him, he must decide to help himself. You said you can not take it anymore, so go now before there are children involved.