discarded, he is being crazy. It's a common reaction to affairs. He wants to experience his freedom, has rewritten the whole mariatal history to support his poor choices, and is demonizing you. He expects you approve of his choices because, in his mind, he's suffered and deserves something. But what is really underneath it, is that he knows he acting terribly and doesn't want to face it.
Below are a few links that may better help you understand all of it: SurvivingInfidelity.com - Support for those affected by Infidelity When a man leaves a woman (Part 1) - Relationship Matters When a man leaves a woman (Part 2) - Relationship Matters When a man leaves a woman (Part 3) - Relationship Matters
At this stage, the best thing you can do is read up on affairs to understand better what he's going through, and what YOU are going through. And focus on yourself. It's easy advice to give, VERY difficult to do when you are heart broken.
I'm sorry you have to go through this. Some day you will be on the other side of it, and you'll be a better, stronger person for it. But the ride sucks.