Hi Ladyofshallot, I'm really sorry about the way you've been treated by him. You obviously had a lot of feelings for him and trust in him but he clearly wasn't who you thought he was. And he clearly isn't worth any more of your attention.
You can come out of this so much stronger though. Maybe you can gradually see this all this as "merely" a lesson to you as to just how unhappy you were in your marriage. Perhaps an "eye opening" experience in helping you see just how alone/lonely/unloved (??) you were feeling before all of this. And with that maybe it's giving you the opportunity to try to resolve that with something real, something really meaningful.
And you know your feelings for this other guy may not have been as much about him/who he was, but moreso about what you were feeling/what you were missing/what you wanted in your life e.g. affection, to hear "............"..............Now those are the things you need to focus on having in your life, not him, as he wasn't able to give you what you needed at the end of the day. He couldn't meet the standards you need in your life.
As to where to go from here with your marriage. Do you really want to continue with it?? If so don't do that because you're feeling that's all you've got/all you have left, that's your only "hope". You can want more, you can stand up and say "enough".
But if you want to work on your marriage, then at least you have a clearer picture of what you truly want for you, what has to change. So maybe start with trying to make your feelings and your wishes, and how you'd like it to be more clear to your husband.
Afterall he may not be so aware of some things, some of your feelings or how important some things are to you. Maybe you can both work on bringing some understanding, mutual caring, and maybe compromises into the way your marriage is to continue?
Alison