I also cheated on my previous fiancé with the guy (“Harry”) and sometimes I thought about him during sex before but after me and a friend were on vacation with him recently, I think about him more often than not when my BF and I fuck. The sex with Harry is just much better and thinking about that makes sex with my BF better. My BF has noticed that I enjoy sex with him more recently and he thinks we have better chemistry now and is kinda proud of that lol.
I hope I can meet Harry again sooner or later but he lives a few hours away so that is difficult.