How can I help a teen who's becoming obsessed with weed?

I had a boyfriend who i had been 5 years with and he actually did all that your boyfriend is doing, i wish you could help him but he sounds like he does not care about what you have to say about. He knows how long you too have been together and he still does not try to al least slow down. I know he told you i will smoke once or twice a week but he might just be doing it behind you back, he has bad influences. Someone who loves you will do everything for you, he might love you but if he did love you as much as you love him, because that is love you are a very caring person, he would slow it down to were he does not need it anymore, for you. I know it sounds very sad but maybe you should leave him as much as you love him because you have to also love yourself before anyone else. You need to stay away also that he sees you are not joking around he probably thinks you are not serious, and that you love him so much that you won't leave him. I know how this goes i went throught this it hurts so much believe me but i'm much better now before i would cry all the time i did all that i could. unfortunately you can't change someone you have ot change yourself first before anyone. But you should not change you seem so caring. I hope this helps you.