dealing with a depressed boyfriend.

It's now been a year and a month into our relationship, and I've finally decided and concluded that my boyfriend is either bipolar or depressed. He's lived a very hard life, so we moved in together away from our home town to start over. But it's become abundantly clear that he's happy with me, but he also misses every thing about our home town, and his depression makes it all worse. Tonight I made the mistake of bringing up the subject of our town and how I noticed his dreams are there, but I'm here. And he has decided he wants to give up his dreams (of becoming a musician, if your curious) because he doesn't want to leave me. But he's making a lot of statements about how his dreams are over and he's worth nothing and he's just gonna work for the rest of his life. There is no pacifying him. Sometimes he just gets into horrible moods and sometimes he's in brilliant ones. I love him so much, he makes me a better person and inspires me, I want to marry him and make sure he lives a better life. But I'm at a loss on how to help him. Ever felt so helpless? I guess I'd just like to know if there's anyone out there that has been in my situation? How did you move past it?