What's wrong with me

I've been with my husband since we were 14, (I'll be 26 next month) there has been a few occasions where we had taken a break/broke up and seen other people briefly (this hasn't happened in over 6 years now and we now have one adopted son and a now an 11 month old)

There was one guy I dated and he crosses my mind regularly, we had a very hard time keeping our distance once I decided to stay with my boyfriend (now husband) but we did and stopped communication completely.

However, he's now in a relationship and when I first found out (seen on Facebook) my heart sunk, and I can't stop thinking about it! WHAT'S WRONG WITH ME?! We haven't even spoke in 6 years.. he's 7 years older then me so I mean I expected him to meet someone and get married etc but why does it feel like this?

This can't be normal?