Welcome to SR!
Good advice above. I am a recovering addict as well as someone who has been involved with addicts. There is absolutely nothing you can do or say that will make him quit using.
There is no "cure" for addiction. If you are an addict, you will be one for the rest of your life. What we recovering addicts learn to do is deal with life without resorting to drugs/alcohol. An addict's initial response to almost anything is to use...feeling stressed? get high. feeling great? get high. feeling depressed? get high. In recovery we learn how to deal with those feelings without getting high. Rehab is only a start in that process.
Once you read around other posts and the stickies, you'll realize that his behavior is very common among addicts. An addict cannot be fully in a relationship with anyone while they are using...it's simply impossible, no matter what they tell you. They may be with you physically, but their mind is elsewhere.
That's why it's so important to focus on you. He's going to do whatever he's going to do. If he wants recovery, he will find it. If he doesn't, he fill find all kinds of excuses as to why he can't do it.
Hugs and prayers!
Amy