21 that wasn't blaming the H. That was telling OP with full faith that she will end in with OM (I believe her when she says she is disgusted with herself and has actually found she dislikes him) - and urging her to work on what she needs to work on.
Which is, her own feelings, that going along with the status quo without ensuring her needs are heard makes her feel resentful, and connectivity with her H. To let him know she really, really needs attention and affection (because she found she was looking for it elsewhere in a really bad way, ie. this is a relationship imperative).
No blaming H.
I still think what Hatty is advocating is dangerous. Learning of betrayal is so devastating that it obliterates rational thinking and it NEVER goes away. This is one thing that is TOO painful.
OP fucked OM on her own, she is learning her lesson (that it is wrong, humiliating, demeaning and you lose your integrity) on her own, and she can work her way back to being a mature, sound human being who truly values honesty and integrity, on her own.
THEN, she can do what she should have done in the first place, which is work on her marriage with a spirit of respect appreciation and humility. Calling on counsellors when she needs to to get him to hear how FUCKING IMPORTANT this is. He doesn't have to know HOW she knows how important this is.
And, OP? Find another job. Urgently. Can your skills be used in another area/different career? Get this cesspool behind you.
I would like to give you a real-life situation why I think Hatty is wrong, and that this is one situation where avoiding the agony is more important than the ideal (of complete honesty):
I was with my friends the other day, and two of them are anticipating going to join their husbands at a trade fair in Germany and making a lovely weekend of it.
I was listening to the smiles in their voices and watching their pleasure on their faces, as they discussed the hotels, and what they were going to do (and the private smiles of their time with their husbands).
The Trade Fair. And the more upmarket hotel than they were looking forward to, where I was excluded and never invited to join, where MY husband fucked his mistress and told her how much he had missed her.
And, you know? At that moment, it didn't matter that he is remorseful, says his affair was the worst mistake of his life, that he is devastated at the damage wreaked, that he is not the honourable man he thought he was, that he knows the most important thing in a man's life is not his career or possessions but his family. It doesn't matter that he hates her, wishes he had never ever ever done what he did.
Because at that moment, I the no longer innocent one, stood as the outsider to their happy, serene bubble, and listened to their pleasure and anticipation, whilst I stood with my private humiliation and pain. This is YEARS afterwards. Do you have any idea what that felt like?
Adultery. The gift that keeps on giving. Don't tell. Stop it, and sort your life out, and work your way back to the living. But don't tell.