How to stop finding someone attractive?

Okay so there is a guy in my class. Our stroy is a bit complicated. We used to be in some kind of situationship. And the most annoying thing is that before I started to like him I didnt find him attractive, now again I had stopped liking him but I cannot stop finding him pretty which is ew. In two weaks there will be a sleepover in school and Im scared I will tell him something like omg I still find u pretty or some bulshit because Im more honest at night. And we arent on good terms. And I dont want to do anything with him so you know. Any advices??