I'm in love with my ex and I can't be

I broke up with my ex-boyfriend last year due to several reasons. One of the main ones was because my mental problems with depression and anxiety I could see were starting to effect him in a negative way. The last thing I ever wanted for him was to feel burdened or unhappy so I decided to break up our 2 year relationship so that he could have a chance at living a happy life and I could work on these issues. Fast forward to now. He's with someone else and happy by the looks of it. I'm still working on these issues and single. When we're together (we're still friends) there's this shared knowing that we both still love each other and a sad nostalgic of what could've been. I can't take this feeling anymore and he's about to graduate college and move away. I have so many conflicting feelings that I don't know what to feel. I want him to leave so I don't have to see him, but the thought of not seeing him breaks my heart. What do I do?