boyfriend gone bad

hey um yea i need help my boyfriend david started to smoke pot and is now a alcholic. He's doin all of this because of the pressure his cousins put on him. He told me he would stop because i'm not all about drugs or alchohol. But even though he said he would stop i'm starting to feel doubt in his words. I need help how can i tell if he's lying and if he really did stop?!!