depression

So I have became really attached to my bf but I feel he suffers from depression. He had a rough childhood and still has some stress under his belt. I try to be as supportive as possible and always be there for him. And do anything I mean anything to be the best caring girlfriend I can. I give him advise and be always supportive. But his depression has him drinking all the time. It got to the point where he almost lost his job. He promised he was going to stop drinking and he did for like 1 month but started again. I really love him but I'm afraid if I leave him he will have no support from anyone. He tells me he needs me and I'm the best thing that has happened to him. But I'm also tired of this situation of him drinking. When he is sober he is the best bf. We have also been ttc for 4 months. I need advice should stay and help him, I really do love him. But I have friends telling me I should not be dealing with this at such a young age and I should just move on. I'm 20 btw he is 24. So what should I do I truly love him or should I take my friends advice? Please help!!!