I'm so glad I found this forum filled with people that can relate to my problem. Where do I start?
Background: We've been a couple 18 years, married 15. We have a 4 year-old girl. We're both professionals in our respective fields, and financially we're fine and reasonably well off. Last year I quit my job for a number of reasons, including wanting to get away from the significant stress of my former job, spending more quality time as a father, and to support my wife in her job (which involves a moderate amount of domestic and global travel -- it was hard for her to travel before because of conflicts with my schedule and caring for our child). My intention was, and is, to go back to work, but that hasn't happened yet, primarily due to the fact that I'm so wracked with this ongoing problem that has paralyzed me to no end. Nevertheless, she is at present the breadwinner.
Our marriage has certainly not been perfect, I think in part because we generally have differing interests and both had busy schedules, but we've never had any really serious issues in the remote past. I love her to death, and she is very kind, sensitive, and outgoing. There was never a major problem with trust or jealousy, and an affair was the last thing on my mind. Frequency of sex has been a longstanding issue since D was born.
Mild Suspicion: A year ago, not long before I left my job, my wife showed me something of interest on her Blackberry phone. She then went to take a shower. I noticed an email on her phone from someone she collaborates with (a vice president, no less, who happens to be quite prominent in his field of work), something to the effect of asking her if she had a personal email address. I didn't think too much of it at the time, since she maintains friendships with many people she works with, and it would not be that unusual for her to discuss out-of-work things (movies, books, culture, etc.) with them on her non-work related email account. He is not based in our city, but across the country, but he travels here from time to time, and they also meet up in other cities for work.
A few weeks later I discovered a string of friendly emails on her personal email account between her and this guy. They were not terribly incriminating, but certainly raised my eyebrow:
OM: Thanks for the document. Did you attach yourself to it? That would be great, so I can enjoy you!
WW: I wish I could attach myself. Keep an eye for a package in the mail.
OM: Are you coming in the package? P.S. This place is not as fun because you are not here.
WW: I wish. Good night.
Other emails I found discussing movies (including the quality of the sex scenes, nothing explicit though), overseas places he'd like to show her, and so on. The conversations appeared to end there. In retrospect, I think they moved their conversations back on corporate email account instead of the personal one for some reason.
At this point, my guard was up. I installed a key logger on her home PC, but unfortunately she uses this rarely for work related communication, and her corporate email requires other authentications that would make it impossible for me to get access to that. Her Blackberry is locked with a password (required by her company), and I can't access phone logs since it's a company phone. Months went by and I was in the dark about whether this was just a-bit-too-friendly working relationship or my worst fear.
The "Hey, wait a minute" moment: Over time in the past year, I noticed her becoming very short with me. Things that never bothered her in the past were suddenly major annoyances. I was criticized repeatedly over finding a job, even though I was the primary person taking care of the domestic things at home, and enabling her to excel in her job without having the stress of juggling schedules/childcare. It was then that my self-confidence really crashed. I had to find out more about what was going on with her.
Suddenly last summer, another string of emails pop up on her personal email account:
OM: YOU are the best!
WW: Your YOUs (in your message) turn me on in a big way.
OM: In what way?
WW: In the best possible way. Big smile. Good night.
OM: Please be more descriptive.
WW: Details: My breathing quickens. My temperature rises. My heartbeat rockets. The rest...for later.
OM: LOL! You are really something.
OK, so I'm thinking this has to be at least an emotional affair (duh!). I have no proof of a physical one. I'm really floored now and in a pit of despair. I can't sleep, eat, or barely function. My heart pounds and I get dry mouth just thinking about it. She's had several work trips since, some of which I and child have traveled with her, and others where she goes alone. I don't know if he is present on all of these trips, but I know he is on some of them. Since the two of them are in different cities, travel/meet-ups are sporadic, coupled with limited access to her communication, it's been terribly hard to gather definitive proof of a PA.
The "Holy Crap!" moment: Last week, I managed to briefly get a hold of her Blackberry while it was unlocked. I found another series of emails that just sunk my heart:
WW: I am sad...I am patiently waiting for (our upcoming meeting overseas) so that I can get a big HUG.
OM: That's all you want?!
WW: I always knew you were a mind reader..I will think of more. A big sloppy X.
OM: I could say what I think about you!
WW: XXXXXXXXXXXXXXXXXXXX
Yesterday, she left for that upcoming overseas meeting, a week-long event. I am just devastated. I don't know what the hell to do next. I've been holding my cards close, hoping to discover proof of a PA, but I just don't know. Yes, I know the signs point to PA, but it's still circumstantial.
Today, we talked for a long time on the phone. I don't think I want her to know that I know yet, but I did say to her that I'm feeling so down because of the way she's been towards me in the past year, and that I feel our lines of communication have closed. I sensed a significant amount of guilt on her part. She became quite apologetic, even tearful, and said that when she returns she will work harder to be a better wife. I did ask her if her lack of affection toward me was the result of "anything else" I needed to know about. There was what seemed to be stunned silence for a moment. Then a denial. She's been calling me every few hours since then to check on me, not typical.
This is no doubt the hardest thing I've dealt with in my life. The mental pictures of this a**hole being there, and possibly being physical with her is consuming me. I hope I haven't revealed too much to her at this point. If I want to save my marriage, I want to do it right. I can't believe I'm stooping to this level, but I'm going out to get a semen test kit to have available on her return (thankfully I'm the household laundry guy). SO embarrassing....
I am not at all ready for a divorce in my mind at this moment. I still love her dearly, and I want to fight for our marriage and family. Maybe that will change, I dunno. There WILL be a confrontation, but I don't know when yet. I am still hoping for some evidence that will abolish the chance of denial and what I guess you guys call trickle truth (TT). I really don't know how she is going to react. I can't even imagine the pain that is going to come.
Sorry for the long first post. Any insights on where to proceed next is appreciated. If the test kit reveals something, then it's time to blow the lid off this thing. If it doesn't I guess I'm going to have to keep digging. I've been toying with the idea of posing as her from her personal email account, emailing him at some point to see if I can get PA evidence. Seems pretty risky though.
I am such a fool to have allowed things to get where they are. It's going to be a difficult week. 
