I don't know if it has already been said but...
I get the impression there are things you are not telling us about this relationship that are pretty important. You are quick to point out the number of times she has cheated on you. From reading your post, it sounds like you don't care if she had feelings for the other men... As long as she never had sex with them then maybe you don't care?
Maybe she feels that you want more than her in the relationship. You verbalize as much by bringing up swinging and trying to turn her poly.
Maybe she is acting out from an emotional low where other men make her feel like she is the only one they want in a monogamous way. However, there is a chance that isn't true if she is openly cheating with another married guy.
So maybe she's got some qualities begging for an open relationship at times... But it sounds like passing urges in between the moments where she feels normal and truly happy... Which I gather might actually be the monogamous moments of her life, regardless of who the man is.
I don't think founding a forced poly relationship between two partners who can't tell the truth is a bad idea. It doesn't sound like she says she wants more than one guy. It sounds like she wants a guy who only has eyes for her, even if only for temporary amounts of time. If that man's eyes wander... She looks for another guy who only sees her. By saying your solution is swinging, you are saying you don't just want her. If she truly feels monogamy is her thing, you should both consider other solutions.
The fact that you are here on a poly site while asking your wife to do open relationship things with you... Sounds like you are the one who is poly and not communicating that well to your wife.
I'm not saying that her lying and cheating is valid. It was definitely not the right move on her part. But as I saw in the first reply... You both need to communicate better.
It starts with telling her anything about you that you may feel you've hidden from her in the past. Anything as simple as "I think other are girls are pretty, but I don't love you less because of it." It will start a dialogue that will either make her feel better or spark some honesty from her. She might tell you that she doesn't like certain things about your relationship. She might at first feel like it is a good excuse to explain her cheating behavior. While there is no such thing as a valid excuse for cheating... Getting her to admit specific problems she has with your relationship will help you both meet an agreement.
I hope I was helpful, I may have rambled some. Sorry!
Last edited by ShpaceEchsplorer; 08-14-2013 at 04:07 PM.