My wife and I have been together for 25 yrs me 55, se 52. We have 2 chidren 16 and 19. I was an open lifestyle thinker and about 4 years ago wanted to explore some sexual avenues(S&M), she was not interested in. I went to a few parties had some experiences and called it a day. When I told her I was going to the parties she asked if she could see another male. I said yes at the time not knowing it would turn into a 2 years plus affair with him,(he was a former patient of hers, a double amputee, chain smoker which she can't stomach, pot head, lived in a flop house, everything I thought she would despise as she is the complete opposite.
She has always handled the finances in the household and I was only clued in by my kids who said someone else was using our Netflix account,
In about a week I discovered the affair was occurring and OM confirmed it.
Trying to satisfy her needs the 3 of us went to a motel on a few occasions. What I participated in and witnessed was extreme sex that my wife and I never participated in at home. She and an emotional connection with him that we never had. I ended it after numerous danger flags went up including someone overdosing in his apartment.
Needless to say I now have images in my head I cannot forget. She claims she is no longer seeing him and does not want to. We are fully transparent and are trying to make things work as we both still love each other. However, after her doing his laundry, cooking for him, banking for him, keeping his clothing and other items in our basement(I was truly blind as I worked many hours overtime with my last job), I cannot believe how she can just get over him since D day was back in July). I check up on her constantly and almost believe she is sincere with me in wanting to preserve our marriage. However, I have not been normal since and the images of what I witnessed just won't fade. This was my fault as well as I did not meet many of her emotional and sexual needs. How do I calm myself down when the images are constantly returning and I'm constantly wondering of her whereabouts as she is off every other Monday and Thursday when I'm at work? Moral of story, don't wish for something you may regret in the end.
Thanks for reading.

Interesting how you gloss over your own infidelity.

You likely need to move to get away from triggers.

You had several affairs, then she had sex with this man, and you had sex with him and her "on a few occasions". What is the point of being married, if you intend to have relationships with other people?

Anyway, she isn't seeing him any more. Give it time and the images will fade.

Given open lifestyle that your marriage is based upon, you can expect this to happen again at some point.