Why do I care so much for someone who doesn't respect me?

A couple months ago, I met a guy and thought it was meant to be. We knew each other in high school through sports, and we're nothing but good acquaintances. Well, after High school, we never spoke again and never really thought anything of him..until 6 years later I was on a group bike ride and started talking to a couple who ended being his aunt and uncle. Well, the aunt gave me his number and we started to talk again...the one problem, he was dating someone at the time. I didn't really want to get involved but both of us became infatuated with each other about how we began to talk again. Well after a month of talking, he dumped his current girlfriend for me. Things were awesome at first, then a couple months down the road, he started to think "whats my ex up to" and started to talk to her again, and cheated on me with her. And I still took him back. Why do I care so much for this person when he didn't respect me with talking to his ex behind my back, seeing her, and cheating on me with her? Part of me still feels we're supposed to be together...but am I being blind?? I finally ended it, but a part of me still wants to be with him. Is fate leading in a blind way??