Gosh i feel so sad for you – 15 years is a long time so i understand why youre sticking by him.
My partners Mum was the same, she said he wasn’t addicted, that he was just medicating his anxiety, yes I agree with her BUT he was self medicating and then he got addicted. Its so hard when families are naive to the fact.
my boyfriend has not relapsed in 6 months now, before that, he was relapsing every 2/3 weeks.. he has counselling every Wednesday for an hour, it is addiction counselling though – see this link, the man is amazing, but its not a quick fix btw, you have to be invested: