I'm currently in a relationship but I keep thinking about my ex...?

I was really close to my ex but it never was really easy between us I miss him a lot and I can't seem to be able to move on and stop my feelings for him. it's been over since a year and a half now but when I see him I still get all those butterflies inside of me. It hurts me so much where he works now was the place I use to go the more often and I can't even go anymore. I'm okay if he ain't around but as soon as I see him I get all confused of my current relationship and what I should do and not. I burned and throw out all of my ex stuff but I really regret it because now I feel like they're ain't no hope left :(