My boyfriend is doing drugs!! PLEASE HELP!?!?

I HATE druggies and my boyfriend was like that too, he didn't even drink alcohol but he's changed. First he got really majorly depressed about the past and his parents and childhood and how he never got to live a normal life and seriously attempted suicide but luckily his friends found out and called 911 and they managed to save him. Then the doctors put him on antidepressants but he stopped taking them and said they don't work and he's been taking Oxycontin, the really strong painkiller to "numb" himself. At first I didn't say anything because I felt bad for him and he only did it once or twice a week. But now he's been taking 2 pills a DAY and chain smokes cigarettes. He doesn't have any feelings or emotions when he's on the drug he just stares at the sky and he says that's how he likes to feel, they take away his pain and help him escape reality. Maybe that's true but chain smoking and daily opioid painkillers at only 19 shorten your life by like 20-40 years. I just want him to be happy and healthy. What should I do? :'(