How to make VIRGO feel better?

So I'm a Capricorn, I've been friends/friends with benefits with my Virgo guy for two yrs now. We started out as just friends because he had a girlfriend. Then they broke up and we started doing more stuff. He was with her for 5 years and I didn't want to be a rebound girl so I stayed my distance.

Recently, he's seeming like he's super depressed. He doesn't know that I know how much he loved that girl but I can tell by the things he posts on social networks. also, she just recently posted a picture with her new boyfriend. I know if he sees that he will flip.

I want to help him so bad and be the friend to him that I was in the beginning before any feelings between us began but he will not open up to me. He scares me with how low his moods are. He smokes a lot of weed lately, his room is a disaster which reflects his life. He sticks to himself pretty much but he does have a lot of male friends which is why I'm not too concerned because maybe he talks to them about his problems. I work in the mental health field so its concerning me he might be depressed and I don't know how to help him, he kinda pushes me away with his short answers and nonchalant attitude.

I just want to know how can I get him to open up or how can I make him feel better without annoying him or seeming like I'm prying into his business? I know why he's sad, I've been through a rough breakup before too. but he doesn't know that I know these things...help

we both have moon signs in aries*