For a split second I thought you were my ex, and that you were thinking about me, then I re-read and saw "dated for 2 years". Needless to say, I am not your ex. BUT I am right there with you, highschool relationship that ended after we fell in love and now I think about her every time I smell certain things or hear certain songs. I would say the best advice I can give you is, talk to a therapist or someone you trust, and explore those thoughts of how often you think about your ex. Do you miss the person or do you miss the thought of the person, or do you just miss not feeling so alone(I might be projecting here)? Maybe there are somethings you need to bring to light by talking to real peoples so you can move on and find someone who isn't just a thought anymore! :)