Am I Just Wired Differerently?

I have had only three relationships in my life:

1) A partner who cheated on me, yet I felt that I made a commitment to him, so after I left, I went back to give it another try. He was not a nice person at all and I finally realized there was no changing that, so I left.

2) We stayed together a long time even though there was not a strong romantic connection, so we eventually mutually agreed to split. This breakup took me a couple years to get over, during which time I wondered, at times, if we made the right decision. I realize now that we did. We are still close friends.

3) (my recent ex) We were together for almost a year when he left me, with no warning and all the blame put squarely at my feet, and I was devistated. I am still thinking about him way too much.

I am wondering how many of you have the same idea of commitment that I feel towards someone? Does this seem normal? I can't even begin to relate to leaving someone so coldly without questioning my decision, allowing for conversation, giving things another go, etc.

Narcissism and sociopathic behaviors are all that have made sense to me in explaining his actions and mode of operating. I am glad I found this site!