guff, give yourself a break, do. There are women who would have been so smitten that they would have accepted what OM said and still continued with the lie because they couldn't face doing anything else. Who knows why but it happens. You on the other hand, have had a slap down from OM - or perhaps he's done the kindest thing and been honest with you - and you've walked away. That takes some guts, lady, it really does.
Don't tell your husband and don't let posters here (with no investment in your marriage) tell you to do that. It's a bell that can't be un-rung and unless you are fully prepared for your marriage to end, don't risk it. Yes, you've made some bad decisions here but they're not life-threatening and there's no need to drop a bomb into your marriage.
Now, what are you going to do about you? That is, after you've finished reeling from the shock. I think the very best thing to now do would be to tell OM that you have no further interest in him now. You would honestly have fallen in love with him and he has told you loud and clear that you mustn't so what else is there to say? Needless to say, you can't be 'friends' with this man now so just break off all contact - and watch your self-esteem soar; it really will.
I've been an OW myself a long time ago and it's a very miserable/euphoric but essentially isolating position to be in. You've managed to break off what was making you feel young and desired because you have an excellent sense of self-preservation. I didn't; my affair had serious ripples albeit it OM's wife never knew. I was single but even so, it was the single biggest mistake/poor series of choices, in my life.
ClopySow and MeMyselfAndI's posts on this thread are platinum-dust. Well worth another read; no nonsense but a kindness throughout like a stick of Blackpool rock... I wish there were more posters like them.
Every day is going to get a bit easier. I know it sounds trite but it's true. Make the final break with OM - tell him straight that you're done and worth so much more - and walk out of his life for good. He's the one who has lost, not you.
Keep posting, you have every right and please - ignore the posters who feel it is their God-given right to kick you when you're down. They look pathetic and spiteful and you won't gain from letting their words into your head. You've done so well so far... take support where it's offered.