Boyfriend with heroin addiction and multiple relapses- what can I do?

[lost]

My boyfriend is a heroin addict. I have accepted that and am trying to support him as much as I can however, I am starting to lose faith.He has tried to kick it on several occasions. He went to rehab, tried cold turkey, and even took valium for a few days and made it through 4 days of hellish withdraw. As soon as he began to feel well again he used again and turned into a monster until he got some. I know it is up to him to get clean. I know he is the only one who can do it and he has to do it for himself. He tells me night after night he is never going to do it again because he sees how much he hurts me and us and that he doesn't want to be a prisoner to the drug. He wants to get married and live happily ever after. Does anyone have any suggestions for me? I am at rock bottom and I don't know if I can take anymore.