boyfriend with depression

Im a pretty happy person, my boyfriend however is experiencing a pretty bad depression right now. He is worried about the future and he's been two weeks off of any substances. (He has substance abuse issues and has started going to therapy)  I want to be there for him, give him someone to talk to. He tells me that everything has become uninteresting to him. He told me our conversation is becoming boring and the se. Is okay well it last but after he feels nothing.  He says that it's him, and that he's still excited to be with me and he was worried that I was thinking he was boring. I brought up breaking up, he reassures me that he wants to be together and he loves me so much but I don't know what to do in situations like this. It sucks nowing that I can't do anything to help him . Has anyone had experience with this ?