Mike, what have you done? My heart aches to think of it. You have real good advice, I would echo a lot of what LilyM said (only I couldn’t say it as well) Talk to a priest, or three or four if necessary. Not to shop for the advice you want, but to be sure you find someone who can help you discern what God wants from you now.
You sound like you are bit of a wreck right now. Your wife is probably going to know something is wrong. I know my wife would. you can’t outright lie to her if she asks, “What’s wrong with you lately?” but know that if you are close to her, that question is likely to come. Be prepared to give an answer that doesn’t hurt her, and isn’t a lie. Or pre-empt with a conversation that you are having a spiritual problem right now and are sorry that you are not your usual self. If you discern later that telling her is appropriate, then you can do that. Pray a lot about that - I thank God right now that I have never had to make that decision.
Be prepared to leave this job, (if thy right eye offend thee…) but not until you have made provision to meet your obligations as a provider. But make no mistake - it’s not the job or the other woman. It was you who sinned and no matter where you go - there you are.
Work on your marriage. Last year, my wife and I attended a worldwide marriage encounter weekend and it has been miraculous. It taught us much about being a sacramental couple in an intimate relationship. It was pretty rocky for a while for us before that. We had grown distant, and lived as if we didn’t need each other. Now we know who are to each other - everything.
Be ready for next time temptation arises, or better yet, head it off. You need someone else male to talk to, on a regular basis. It is good to have a friend who you can share real, personal, things with that is NOT a woman. A well-catechised member of your parish who you respect, or a spiritual mentor, clergy or otherwise. A well-timed conversation about resisting this woman’s advances last year, might have saved you some hurt today.
It’s good to have a man you can share insecurities or temptations with. You don’t have to mention infidelity, but “impurity” in general covers it. Mutually supporting each other, we strive for holiness. Sounds corny but we need it.
Having this person in your life makes it harder for that sympathetic female to “make inroads” as you described it. We’re going to want to talk to somebody sometimes, about things we don’t want to worry our wives about, or even tensions at home. It is not appropriate to share these things with a woman unless she is your sister. And your sister is probably not someone to talk to when you find yourself fleetingly tempted by a short skirt or a magazine cover at the supermarket. We find it easier to be open and vulnerable with women, but if we’re going to be emotionally intimate with anyone other than our spose, they cannot be of the opposite sex. It has to be someone who will support your marriage, not drive a wedge into it.
Confess and receive the grace of reconciliation, pray a lot and remember that none are beyond his forgiveness, and that all of us have, at times, sinned grieviously.
I’ll pray for you, and your family.