Retroactive Jealousy

(31 year old male) I struggle with retroactive jealously. It’s irrational and I know it is but my mind can’t seem to stop the mental theatrics. Me and my current girlfriend of just over a year went to college together so we know of the same people. I was in a long relationship with my now ex during that time, I never knew my current girlfriend during those years in college. Recently, through a transparency discussion - I found out that she had sexual history with someone I consider to be a friend. Not in my direct close friends, but someone that I had regular interaction with. She obviously did nothing wrong, I was with someone else - we didn’t know eachother, shes got just as much of a right as me to be with someone else in that time of our life. My ocd doesn’t care and it’s exhausting. I find myself ruminating and going through mental movies of what they did together in the past. This is admittedly paired with my own insecurities which is the worst part. I have always considered myself underweight and it’s easy to fall into comparisons with her previous partners. Another part of this is, I am a mixed man (black and white), who was raised by a white single mother and I had little to no connection with my father - this has always left me with a feeling of disconnectedness with my blackness. Paired with I never had the mental strength to progress in sports past recreation, it’s really tough to find out that my now girlfriend had previous intimacies with overseas basketball players and the friend I mentioned above was at our college for football. I fall into allowing myself to go down the rabbit holes of being inadequate, or the assumption that those previous people must be bigger than me, able to satisfy her more than I could? She’s done nothing to feed this thought, and thankfully I haven’t gotten to the point where I directly ask size comparisons. But my mind won’t let me just let it go. It’s clearly associated with childhood insecurities. I don’t get complaints in the bedroom, I’ve always considered myself above average but it’s easy to make assumptions because of the extremes of pornography. I recognize how pornography is an issue and have completely stopped watching now that I’m faced with this. I just wonder if this is something I will ever be able to get over? This girl is perfect for me in so many aspects, it feels stupid to be this caught up on something that objectively shouldn’t matter. She may have had dealt with more people in the past than I’d like (12), but she still is very submissive to me and it doesn’t feel like there is any residual tendencies that she adopted from other men. Such a long post, and I could go into more context but I just wanted to post my struggle because I know I’m not the only one out here dealing with this.