Relationship Issues

Hi, so Im in a predicament which is very...odd. I'll try and explain as best as I can, my wife and I have been together for about 13 years, together since highschool. There was a period after highschool where she cheated on me, and broke up with me. During this period I did a lot of self improvement, physically, mentally. After a period of time my now wife and I connected again..and 5 years later now we have our first child and are married. I love her I really do and she's been nothing but faithful since the day we got back together. The issue is that she cheated on me with my high school bully, and the whole reason she did so was because she wanted to have sex with other people. I at the time of the break up was unaware the person she was with was my high school bully, when we reconnected, obviously the information was laid bare. The issue im facing..is that I've forgiven her but there are times when..my brain just goes down memory lane and all I can picture is my wife and my high school bully..I don't know how to..get over it..I love what we've built together but I guess because of the trauma there's a deep rooted part of me that just thinks it wasn't fair that she got to do whatever she wanted and then come back. I didnt have time to even date or focus on women during our break up because I was so focused on improving my life. Im just so stuck about how to feel, there are days that I am absolutely mentally not there because of these thoughts I bring it up with my wife and all I get is.."I was young and dumb". Some days I feel ill never actually get over it..does that mean I should end things now and hope for the best..my trauma and hurt make it so hard to move some days...and other days I can go months without a thought. Im so ashamed that I can't be the bigger person and just move on..but my mind always goes back to saying its not fair that you got hurt so badly and its not fair that she got everything she wanted. Why am I like this?