Hi Ali51
How much do you love him and Do you trust him? Do you believe that he is no longer sniffing? If he is drinking more then is that also a problem? He clearly needs help with his mental health and there are all sorts of therapies around that do not involve taking medication. But he would need to do this himself.
Maybe you could speak to a professional (counsellor, doctor etc) and get some advice and proper facts about addiction, no matter what the addiction is somewhere inside the body is the person you love. Sometimes it helps to understand addiction and what is going on in their bodies to make them crave it. At the end of the day you can support him and point him in the right direction but only he can make the choice to help himself.
I hope this has not come across too uncaring, every body on this site will be feeling your pain.
You sound young and in love, do not get so absorbed in his problems that you stop looking after you.. You matter too xx