A large majority of the people that our spouse hook up w/are beneath their normal standards. Beauty is in the eye of the beholder, or so they say. To our spouses, these people do not know their history and are willing to believe anything that they are told. Our spouses want fun, freedom and the ability to come and go as they so please. They are reliving their youth and yes, telling these people all of their thoughts and feelings. The OP is there listening and validating everything they say and they actually believe what our spouses tell them. The OP is nothing more than a band aid and hopefully at some point, the OP will tip their hand and our spouses will see all of the warts and imperfections...but it takes lots and lots of time for this to happen.
We all become fixated on the OP because we are trying to figure out what they had that we didn't. They are nothing. We had and spent the best years of our lives w/our spouses. These OP get the used up part. Trust me, many of them can spot a MLCer a mile away and figure that they will enjoy the ride of the MLCer's spending and having a good time until the money has run out.
Right now, you are very new to the crisis and it's going to take time to settle down and come to realize that you are the prize and your spouse is the fool in all of this because he sees something that no one else sees. Every time you think about that ow, find something else to do. She can't compare to you.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.