Going through all my past relationships and for some reason looking for things to get upset about?

Broke up with my ex about 2.5 months ago, had two flings since then. The last one ended quickly but painfully for me because she didn't think we were serious at all, and I thought we had a future. For about 3 weeks I dwelled on that and was pretty upset. I'm finally pretty much over it but then a few days later I started thinking about the girl before that who was nuts and kind of used me and got upset. Now I'm dwelling on my ex wondering if she also was using me or was as faithful as she seemed. Ugh I feel like I'm being ridiculously cynical and crazy because me and my ex had a really good relationship. Anyone gone through this? Any advice?