how do i deal with a boyfriend and drug problem?

i’m 15 and currently dating this guy. we have been together for about 3 months now, and i’m really attached to him. unlike other boyfriends, i can tell he feels the same towards me. being with him has made me really happy, but during the first month of our relationship he opened up to me and told me he was struggling with drugs. i’m not very educated on this kind of thing, never really dealt with addiction. see it would be one thing if it were marijuana, but he’s going harder than that. meth, coke, he’s told me he did heroin before... he wants to stop and i know someone who’s hooked on these kinds of things most likely can’t just quit cold turkey. every time he talks about it i just get really angry with him. i don’t know why? i feel horrible because i want to help him out of this, but i don’t know how, especially when i keep lashing out on him for something that’s not easy for him. he told me the reason he started was peer pressure, which i believe. i’m happy hes honest with me about this rather than hiding it, but i don’t know how to deal with it. does anybody know how i can support him and help him get help? and maybe how i can stop being so angry at him for this? it’s hurting me, too.

update! i realized a lot of people commented on this thread and gave me some really great advice and i appreciate it! after some long talks and a few arguments, but nothing too serious, he decided he was going to discuss his problem with his parents and let them decide what they think is best. i’m being patient with him, it’s not easy but i’m trying. some might think i’m being foolish by not leaving him, but i want to get through this with him. i see a lot of potential in him and he has very good qualities that other guys i’ve met haven’t. he’s extremely supportive of everything i do, pushes me to do good in school, he calls me in the mornings to make sure i get up and i’m not late. i’ve been stressed lately, and clearly he has too, i think right now we both need each other, even if we don’t have that fairytale happily ever after ending, i still know that i love him. i would hate for someone to leave me in the state that he’s in, so i’m staying.