<human>: Summarize the given text in a few sentences.

Just some background; I'm a 23 year old male who has had maybe 3-4 relationships in his life.  The current and the latter being the issue at hand.

So anyways, about 1- 1.5 years ago I had a relationship with a girl I had known for about 2 years prior at college.  I fell for her very quickly and by the third month we had already told each other we were in love.  Things were great until right before we were about to graduate (four months in), where something just went sour.  There was a week we were both busy and couldn't hang out with each other, followed by another week of more distance on her part.  Once I asked her about what was going on, she said she couldn't explain her feelings and was sorry.  I was very upset and that was the last contact I made with her.

The following few months were tough, but through friends and other hobbies, I eventually got through it.  I convinced myself that I was over it and happy with my current state.  I then got into my current relationship 6 months later.  

However this ex has currently started to pop up into my dreams and occupies a lot of my thoughts, recently happening more.  It's mostly about what would happen if we bumped into each other again, as we live in the same city/state.  Or in my dreams her explaining why she left or that she wants me back.

I really don't want to have these thoughts anymore considering I'm with my current girlfriend.  Sometimes I catch myself comparing my current girlfriend to this ex-gf, and thinking of some advantages/disadvantages in that aspect.  

It's starting to really bother me and I'm starting to hate myself for doing it.  The lack of closure is probably the reasoning for it all.. but I can't seem to get over it regardless.  

I haven't told anyone this and the reason I'm asking is, for anyone who has been in this situation before - how did you handle it/move on.
<bot>: ex-gf 1.5 years ago broke up with me, no closure, got new gf, can't stop thinking/dreaming of ex, I'm an asshole, etc.