I'm sorry.
I was about to recommend to be upfront as well.
This might not feel good to hear right now, so I don't mean to sound insensitive... I just think it's important to always be upfront.
It's nothing to be ashamed of and the more people talk about it the more educated people become.
If he left bc of depression, he wasn't probably the right guy for you.

But I am sorry, I realize how difficult it must be.

Hugs.