Hi Diggity11, welcome, and sorry you find yourself here.
I have to say, when I read through your first few paragraphs, it was almost a copy of my relationship with my WW. Both HS sweethearts, both our first and only sexual partners, etc. We started dating in 1996, married in 2004, first and only child in 2006.
My dday was July 28, 2015. I learned of her recent PA by snooping on her tablet, found one email that couldn’t be misinterpreted, then found the video she sent him. Ironically, reading the words my wife sent this guy spelled it all out, but for some reason, it didn’t register with me.....until I saw the video, I couldn’t ignore that! When I confronted her, she admitted to a ONS prior to marriage, while I was away for the weekend. We fought, ironically, about my lack of commitment.
Anyway, you obviously feel you don’t have all the details. I felt and still do feel like I don’t have all the details either. It took 3 years and threats of divorce for my WW to come clean with me. This TT, over 3 years ,was exhausting.
After dday, my WW had answers for everything, except, things just didn’t make sense to me. What she was telling me didn’t align with what little evidence I had. Guess what!! I was right, there was more, there always is.
I can tell you that no matter how much time passes, these unknowns will eat at you. They probably have been since you found out. I wanted to believe my WW, I wanted to kill her AP, I wanted things to go back to “normal”.
As I got more educated (thanks to SI and other forums), I began to grow a spine and wouldn’t let things go. I asked her the same questions over and over again. She maintained her story but she finally realized I wasn’t moving on, so she let out more truths over the next couple years.
I would suggest a polygraph. Your WW might come back at you with a bunch of reasons why it’s not needed, she might gaslight you, deflect, etc., but this is really the only way we as BS’s have to verify our cheating partners story. Many folks go this route and end up with a parking lot confession, or a confession to the polygraph examiner. Regardless, it can be a good tool to get to the truth. The fact your WW’s story doesn’t match what you have been told is not uncommon. WS’s minimize and withhold information to “save you more pain”, which is total BS, it’s all a means of controlling the situation. My WW was deathly afraid of all the truth coming out and that I would have left her, so she made the choices to withhold info that I wanted and needed.
I realize it is a long time ago, similar to my situation, but this is the type of thing that doesn’t go away. If your WW is confident that she is telling you the truth, she should have no issues taking a polygraph. In fact, she should be enthusiastic about “clearing her name”, but I doubt this will be the case.
I suspect she would say “haven’t we moved on from this”, “I’ve told you everything, why do you keep digging up the past”.