[¯|_(ツ)_|¯]

Do you think it's worth sitting down and talking to him about this one last time, and letting him know that you want more than a casual discussion? You can let him know that you realize this happened a little while ago, but it is still on your mind. You can also let him know that you are worried that the friendship is starting to deteriorate a little bit and see what he says. Make sure that you use "I statements" and try not to accuse him of being malicious, because this may put him on the defensive.

If he doesn't take it well that you want to talk things out and either laughs it off, doesn't take it seriously, or argues with you, maybe it will be a good idea to pull out of the friendship. But right now he probably doesn't know what is wrong so he can't try and work on it with you, if this is something he wants to do. The reason I say this is he seemed surprised about your depression at first, so he may not know that this is weighing on you still.

If you do have to end the friendship, either because you don't feel it is worth it to try and repair things or because repairing things doesn't go well, don't feel guilty. Sometimes friendships unfortunately run their course. It happens in life, and even though it hurts, you deserve wonderful friends.