If you can't stop thinking about someone?

There was a guy i was talking to. We weren't officially "dating" but we may as well have been. He would call me everyday, text me everyday. We would talk for hours and hours and hours. I ended up finding out a lot of things that made me realize we weren't gonna be good together. But since then, I haven't been able to stop thinking about him. I don't know if that's just normal, or if it means I should talk to him again?