I think he just needs to figure this out for himself and most importantly, spend time with HIMSELF. Admitting he's an addict is huge, and now he has to take the steps towards recovery, and unfortunately, that may mean cutting ties with the relationship.
My ex used for 5 years, has been sober for two. He pushed me away after telling me about his past. This all happened within this past month and I've been researching addiction since. (well, stopped these past few days) Using heroin (his drug of choice) every day for 5 years definitely had an impact on his mental health, whether he wants to admit or not. I eventually had to end things with him....and, you know, sometimes you really have to let people go. I've been trying to understand addiction, but it's something I never really will 'get'.
Your ex needs this time for himself, without distractions. He has to come to terms with who he is without the drugs, how to live without them etc. I'm sure he appreciates everything you've done for him, but you gotta go your separate ways and get right by yourselves before you can be right together.