Just to clarify there is a typo and we actually we're dating for 4 months, which was basically the entire summer. To answer your question she just felt that things we're getting weird between the two of us and that it would be better to go back to being friends. I have had no explanation beyond that. I basically agreed and that was that.
We stil do stuff together regularly, the only thing that is different is we are not "dating." I'm not sure what to make of this and that is main question. Because I don't seem to be getting anything negative from when we broke up, just taking it down a level...or something.