Welcome to our forum.
I'm less concerned about the idea of polyamory here than I am about the sneaking around and covering up so that the spouses can't consent. Even if her current affair ends, how do you know she won't start another affair with someone else?
You need more honesty and communication in your relationship. You can consider polyamory, but there's a right way to approach that kind of life. "Opening Up" by Tristan Taormino is a good book to read; maybe you and she could read it together and discuss your feelings about each part you read.
After you have gained some knowledge about polyamory (and other forms of responsible non-monogamy), you will proabably be in a better frame of mind to decide if it's something you can live with or around.
We have a Golden Nuggets board
that you might want to check out. It discusses a lot of the basics.
Give it some time, I guess is what I'm saying. Learn some more before you make any big decisions. Post thoughts, questions, and comments. Ping your threads with new posts if they get lost in the shuffle at first. Get feedback, and ponder what the various folks here have to say.
I hope your wife gets serious enough about polyamory to at least stop having secret affairs. I sympathize with your dilemma, you're getting the short end of the stick right now, and that's on top of the one-man one-woman programming that we all receive.