There is stuff about your relationship that contributed to making him unhappy with it, and where any such fault lies with you, then it behooves you to make improvements in you as a person, for yourself and for your relationship. Your husband has to grow too, but right now he doesn't see that, and doesn't clearly see the role he played in his own unhappiness. After all, it's his marriage too and he was a participant in it and contributed to its down cycle. And when conducting a secret affair, as he was doing, his emotional involvement in the marriage is null, and so without realizing it, he therefore sabotaged it, keeping it in a down cycle.
It's not unusual for spouses who are caught to deny or lie or tell you you're imaging things. Sometimes, even when fully remorseful, it's because they don't want to hurt you with details. They don't understand your need to know, the need to feel that there aren't any more secrets. They may feel guilty as well, and telling you more about their affair hurts them to do so, making them feel guiltier. So, you have to pay close attention to your husband's actions at this time, more than his words, because by his actions you will know if you can trust him. Be prepared for the worst, while hoping for the best.
As crazy as this sounds, as hurt as you are, it's all about him right now, not you. He actually needs more help than you do, and you know how much you're hurting. So don't get wrapped up over him, keep your mind on your well-being. You've also been advised to read through the book and apply it. The newcomers section has some articles you can read as well that should get you on the right path. Take it slowly, have patience. Let us know how it goes.
