I wish I could tell you, because I still don't know. XW said a lot of things but they were either evolving or unrelated to each other (I didn't load the dishwasher the right way, I didn't appreciate the finer things in life, she didn't want to be woken up early on the weekends, she finally said she just wasn't happy). There were no other issues like an affair, addictions, money problems, etc. When I was deployed though, I told her that I thought I wanted to start a family, something that we had both agreed on when we first started dating that we didn't want (I realized after everything was said and done that I still don't want kids).

Like I said in my original post, I think she was seeing someone from work. There were pictures that she had taken from work parties, work friends' weddings, etc where she was standing next to the same guy. These events were weeks and months apart too. All of her work friends that she socialized with (starting after I deployed, never before) were single. I'm not sure if anything physical developed, since she always denied an A and never told me about her friends and what she would do.

I hope that this helps you to make an answer.