Hi, Stu...
I'm replying again because you asked me to. I hope that I'm not pushing you too much. I'm just going to tell you what I think again and hope it's helpful.
What I'm reading here makes me think that you have insecurity issues that stem back a long way. Probably as early as high school. That insecurity seems to come from observing a certain social expectation for you to be what you've called an "Alpha male" which, from your description, appears to be a man who is aggressive sexually, hooks up with many women, commiserates with other men about their conquests and generally, frankly, treats women as sexual objects and with a great deal of disrespect. You seem to have been wired differently. You took your time sleeping with someone you cared about. You didn't actively participate in the antics you saw these other men engage. You played by rules that you were comfortable with and showed you had a great deal more maturity and character. However, again, that you weren't sleeping around or engaging in jock culture seems to have made you feel like an outsider.
Your continued descriptions of the OM... his body, his behaviors, his "alpha" status, your encounters with him, his "fluids," etc is you participating in an act of comparison with/against yourself. You don't know how to measure yourself up to this man. Potentially all of your life you've felt inferior (the beta male) to these kinds of men (the alpha male) and now you have to contend with the presence of one of these guys acutely in your life and your M.
This is just a preliminary guess-- but it sounds like you viewed your wife as the kind of woman one of these jocks would have considered a conquest. But you had her. Until you found out that she had, in fact, slept with a man who symbolizes all of those things you once found detestable. And so this has made you question everything.
In terms of advice... I agree that you need to start thinking about what you want and need here and try not to mentally subordinate yourself to this man in your mind. He's long gone, Stu. Certainly you're going to need to replay your encounters and the mind movies of him with your wife will take a long time to set aside (I speak from experience). But don't let insecurities from the past cause you to stagnate now and spin your wheels. Time for you to find a way to feel safe and move towards a healthier view of you, your wife, your marriage. To learn to process these thoughts. To figure out how, or even if, you can communicate with your wife.
I'll get personal for a second on the subject of your wife. While everyone is different, I can sense that I may have some similarities with her worldview and, at this stage, contemplating what she could have been thinking is something you are going to do anyway... so maybe this will help you process. But remember that whatever I say here, I'm not a substitute for your wife.
Before I met and M my X, I was a pretty attractive girl and I tended to date the kind of alpha males you are describing. Body builder/professional athlete types. My X was nothing like that. He worked out a lot, but he was never going to have a six pack. And he was handsome... but sort of in a professional/professorial way. He was more of the brainy type and he wasn't going to win any Adonis contests. When I met him, I wasn't attracted to him in the way I had been with other men. With other men, I was turned on by how, to use your term again, "alpha" they often were. That's not to say I allowed myself to be degraded by them... but if they took charge a little or wanted to try something different sexually, I was into it because the level of engagement with them was different than it was when I was in a relationship with someone who was my boyfriend. With someone I was trying to build a life with and wanted to establish full equality and respect. With some of these other guys, I might go on a date with them because I found them attractive, sleep with them, keep in touch with them for a few weeks or months... but then move on. Because I never wanted to end up with one of these guys as a partner. For my husband I wanted someone like the man I thought I married. Serious, compassionate, intelligent, thoughtful, etc. (It turns out my X was more of a broken person than I realized! But that's another story!)
In any case, I remember when my X was pressuring me to date him exclusively and head towards M. I was very young and, although I loved him, I was unsure about marrying him. I wasn't sure if I should keep dating. If he and I were better as friends instead of lovers. But then I thought, I could do a lot worse than marrying my best friend. Someone who had shown me that he wasn't one of these disgusting alpha males. Someone I could trust. Who would be an equal partner. Who would be a good father. So I did it.
I'd say it took me a few years, but I eventually came to deeply, deeply love my X and I never regretted my decision to stop being the cute girl who hooks up with men who are full of themselves. I wanted the kind of intimacy I had with my X where my sexuality wasn't viewed as something to be obtained. It was something to share.
When women are growing up in the kind of culture we are in, we are given a lot of conflicting messages. We are told we have to look a certain way. Be available to men in a certain way. Much like you feeling pressured by the jocks in high school, we feel pressure to accept the attentions of these kinds of men to feel like we have value. It can be very, very, very difficult for a woman to negotiate these waters. So when your wife was feeling like your dating relationship was stalling and got attention from an "Adonis"-- I can understand why she might have felt pressure to go on a date and, when he came on to her, to go along.
But when you called and asked her to marry you... she made a choice. She chose not to be that girl anymore. To choose a man who wouldn't take her for granted. Who wasn't just after her as a conquest. You valued her more. And, if this story remains the same, it sounds like she left that other girl behind in that diary and, for 10 years, has been a wife to you. She may not even relate to who that younger, impressionable girl was. It's even possible she may view herself as victimized by that man and she doesn't know how to process it. I can imagine all kinds of reasons why she's reluctant to open that part of herself back up and look at it.
That doesn't mean she shouldn't for your sake. But somehow you two need to figure out how to communicate about this. This is both triggering so many issues for both of you that have less to do with her one night stand a decade ago and so much more to do with how the two of you relate to one another and understand your roles in your M. And you both clearly need to do some work separately to deal with your individual problems and figure out how you want to proceed in the M. There is something that people on SI say a lot: your old marriage is dead. And it is. You can't go back to the blissful ignorance of the past. The good news is, it sounds like all of the piece of this new reality are on the table-- down to her diary. The "bad" news (which can be good news) is that you now have a lot of work to do to contend with it.
Okay, this is a novel, so I'm going to wrap it up. I hope this helps a little...
[This message edited by PhantomLimb at 11:27 AM, March 9th (Sunday)]