I'm so tired of helping my depressed best friend
I'm sorry to hear that. Why do you think you're tired of helping them?
I can't do anything to stop it, but I know if I don't help him the depression will get the better of him.
Having to help your depressed friend sounds very difficult, so it makes sense that you'd be tired because of it. I think you should try to help your friend talk to a psychologist about his depression because they're well qualified to help, and so that you can get a rest.
I know it's still early but I don't care anymore.
Even if you are tired, it's still recommended that you care about your friends, specially in the time of crisis like depression. If they do not get better, you will lose them and you will just end up being lonely yourself because you loset a friend.