How to deal with a depressed boyfriend?

Hello
I'm 22 and I am in a relationship for two and a half years now; I have this very intelligent and gentle boy as a boyfriend. We have different nationalities and live in different countries - I'm romanian, he's french; we 're students, we're normal people, we're both ambitious and hardworking. We've met during a summer project and my boyfriend came very often in the country since then. We thought we had a strong, reliable connection, we thought we were in love. After one year, we broke up for three months, and meanwhile I realised I was in love with a very close friend of mine, but there were no chances for me and that friend to be together so I dropped it.
Few time after, we - me and my french bf- got back together and tried to rebuild what we had. Few months after that, his dad committed suicide, and that brought us closer, but afected him and his family in a very bad way. I moved to france, for us to be together, and got closer to his family. They're all wrecks, even after one year now. I never dealed with such a situation before, nor even observed. My boyfriend is getting more and more depressed and blocks himself, and me, from simply living and enjoying life, as good or bad as it is.
I really care for him, but I'm not sure I love him, and I don't know what to do anymore. I'm trying to be supportive but it works less and less, and I'm afraid of getting depressed, too. We both are getting worse, and relationship is going down, and I wish I could stop it, but I can't just run away and live him in the mess he is today. It's bad if I stay, bad if I leave and sometimes it's getting insane; it started to affect my studies and probably a great deal of my life. Please, if you've been in a similar situation, please tell me about your xperience, maybe it will help to find a solution, or at least help me find the patience to help my boyfriend.