DG, so many of your friends here on SR have already said wise and good things in response to your thread. I only want to add a couple of personal reactions:
I admire you both for waiting to confront your bf, and for doing it. You thought it through for a long time. Of course you'll second guess yourself now. With relationships, there's never a "right" thing -- but it was the needed thing for you, because you've already moved on from him as a boyfriend, no matter how fond of him you remain.
It's natural to wonder if you didn't try hard enough and wonder how you'll get along without him -- but as a substance abuser, you have to work to stay in the now. Those regrets and projections can spiral and lead you to a drink or drug. You've set out on a path -- keep walking it one step at a time, concentrating on keeping your head and your feet facing the same direction.
My guess is there's a part of your head that's telling you that you should pick up over this. It's the perfect excuse/opportunity/memorial/finale. That's a LIE. The best way you can show yourself you're acting as well as you possibly can, is to act with sobriety.
We're all thinking of you with pride and warmth. (((DG)))