What occurs to me about your situation (if you can forgive this "insight" at such a distance) is simply that - you didn't really know your boyfriend before he went to rehab, and you don't really know him now either. If he was an active user during the time you were dating and you didn't know it, then the two of you didn't really get to know each other. And for sure you won't be becoming more emotionally intimate for a while now, either. His focus during recovery has to be on himself, full stop.
I wish there were some way that the two of you could have a healthy interaction but that's probably long away in the future. In the meantime, as the others have suggested, the one person in all this whom you can potentially influence is yourself, so that's a good place to start.
Good luck to you,
Jane