Sorry this post is lame and I wish I didn’t have to make it

I broke up with my ex in June and I finally stopped replying to his breadcrumbs in August. It was 4 years of bad mental health, drug addiction, fighting and love. I know he’s bad for me, he’s blocked on every single thing and hasn’t once reached out since I told him to stop in August. 

I thought I was slowly getting better, getting over him, thinking about him less but then in February I saw him walking on a street by my school and I lost it. I really wanted to drop out of school so I wouldn’t have to go to the city again but my therapist helped me through it. Ever since then however he’s been on my mind pretty much non stop. All the effort I made getting over him is gone. I’m thinking about him, fantasizing about reconciliation, all that happy horseshit. Except now I’m really sad because we aren’t together.

Can someone help me or give me tips on how to get back over this. (I’m a big black/white thinker so when I end any kind of relationship my brain just pretends their dead until I feel better which I think was happening but then I saw him and I know he’s alive)