My feelings are so weird. please help.

I dated this boy, lets say his name is Zane, for 8 months. Serious relationship, no fights and i broke up with him, January of 2018. He lives in the town west of me, about 5-10 minute drive, so I see him somewhat often. I still care about him so much, you have no idea. So I care about him A LOT, and EVERY TIME i see him with other girls or my friends (all of my girl and guy friends are friends with him) I get jealous and I miss him so bad I want to cry. But the thing is, is that I can't see myself marrying him and I feel that way so much that that's one of the reasons that I haven't gotten back with him. Can somebody please! help me sort my feelings out.