wow !
This is some thread ..
I do have one question
You said your seeing a T , was it because of the lack of sex your getting ?
If so then why on earth didn't the T say to you I want you to ask your wife to join us and talk about this so she/he can view both sides and give you both the help you need .

I think what you need to do is see a marriage counselor , your wife needs to see how you feel and I know you said you talked to her but maybe she will understand better by having a counselor there as well . Maybe she will open up more and tell you what is really going on .

But to have an affair is only going to cause more problems ... trust me I know , I had a few and yes I told my husband he new about it at the time . I don't regret it but I won't do it again .