if he's shooting up IN your home, buying methadone off the street, AND drinking, he IS using. you aren't stopping him from anything. I know you THINK you are, but you are enabling him big time. you were willing to GO WITH HIM to buy more alcohol!
you talk about NOT ALLOWING him to shoot up, and not allowing him to leave. do you plan to be his jailer? are you going to stay home and watch him 24/7? your rationale about addiction is pretty skewed:
I don't think he wants to use to get high right now, he wants to use to feel better
you don't have your BF back, you have an active addict on your hands.
if he really wants to get better he will stay here.
you are not an addiction specialist, nor is your home a detox center. if he REALLY wanted help, he'd DO something about it. if he can call YOU, he can call for some type of professional help. and he needs a lot more than a three day detox....but that is all on him. as long as he knows when it gets so bad he wakes up in a stairwell and you'll send him money and take him in, he's not likely to make the right call.