Thanks for all your help. We've arranged to do counselling with a poly-friendly counsellor. This person is far away, though, so we'll have to do it via Skype. Which I think is fine. We live in pretty small, conservative area.
My wife's behavior began to change a lot five years ago after our girls were born. She would get stressed out to the max all the time, and began to take meds for depression. She is also somewhat Bi-Polar, and took some meds for that, too. She would often scream and slam doors, and would continue to occassionally spank even though she knows my objection to corporal punishment. She would occassionally curse, too, in front of the children, and on really bad days would say things like "Being dead has got to be better than this", and "When you girls whine it makes me want to stab my eyes out!". She would often scream at the girls right in their faces.
After she had her affair in late 2010 we attended counselling. Over the course of a year things got much better. The primary things I objected to about the affair were not the sex, but the deception. She hid the emails, texts, etc. from me until I stumbled upon them, and even then she increased her deceptive methods until I was able to I was able to do enough detective work to find out. Only then did she fess up and agree to counselling.
About a year or so ago she was the one who suggested trying swinging. After our previous experience with that couple she had known since high school (a very positive experience that ended when our girls were born), I was actually excited about the prospect of trying it again, this time a little more formally by joining a popular swinging web site. We had a few encounters, one of which didn't go anywhere, and another that worked out pretty well. Usually, as is the case in the swinging community, we did same-room swapping. One particular couple also enjoyed separate room swapping, so we did some of that with them. Eventually my wife decided she didn't much care for the same-room play, only the separate room play, saying she just felt uncomfortable being watched. We talked about this for a while and decided instead of being swingers to open our marriage to take on friends with benefits.
This worked out a good bit better for her, as it is about ten times easier for women to find FWB's than it is for men. She had about four FWB's, and then one in particular she started seeing much more regularly (about twice per week). She then admitted she had started developing feelings for this guy. The non-stop texts between them continue even now. That's when we started discussing the idea of polyamory. I agreed to try, even though I don't currently have a partner (although I could see myself falling in love with another).
The last few weeks she has been getting colder and angrier. In addition to not wanting to have sex with me, and moving into the guest room, she has talked incessantly about how she "doesn't feel the same towards me", and talked about wanting to take a vacation with this other guy, and not wanting to take vacations alone with me. She says she wants me to talk about my feelings, but that usually ends up with her yelling and cursing at me. When I questioned her about wanting to go see him at 2:00am on New Years night after we had been out partying with other friends, she got really angry and talked about how she can do what she wants when she wants. When I remind her that she is treating this new guy a LOT better than her husband of 15 years and father of her children, she says things like "Our marriage is only on paper! Get used to it!", totally ignoring how our marriage is a commitment she made and the 15 years of mostly good times we've had.
I feel her relationship with this guy is clouding her judgment and is leading to a lot of this "re-writing of history". Complicating things are the fact that she earns a LOT more than me ($175,000 vs. $50,000), and the fact that two years ago she got bariatric surgery to lose weight, and now she's thin and I'm not. She also got a breast augmentation (that turned out great, BTW, not very fake looking like a lot of those out there). I almost feel like I've been used during those tough years of the children, enduring the night-time wakings and diaper changes and tantrums, and those lean years when she was going to grad school when we got by on only my income. I loved her through all that, even when she weighed more than me. I sort of feel like now that she's "new and improved", she's tossing me aside for a better model.
I'm sorry for the rant. But I think it's been therpeutic.