Boyfriend and our 2 month old childs father is addicted to roxies? I need help! ?

OK... My boyfriend and I have been together for four years. We just recently had a precious son who is now 2 months old!! HE WONT QUIT! He is shooting up roxies? and has been for about a year now. I never realized his habit was so bad untill now. I have never done drugs so I dont know what its like but both my parents did for years ... who are both now clean! I just dont know what to do? I dont want to leave him ... But I know I have to do something for my sons sake. Hes like a broken record ... saying hes going to get clean, he cant take spending all his money on it, he wants to be here for his family ..... Blah blah blah. He went to rehab for about 5 days but then left. I just feel like were the only thing keeping him from not killing himself? I cant keep seeing him do this ... Putting his family second ... His son needs his dad ... I cant help him anymore ive done all I can .. And I realize he has to want to help himself ... I just dont know what to do at this point I cant take it and its not fair to our son. I am going to go into depression or something from all this. I dont want to leave I juat want him to wake up. Please help me!!!!!