After 12 years of marriage, you learn that love changes. I don't love my wife any less than I did 12 years ago, but I certainly love her differently. Have I met women at work who I have a connection with? Yes - because that's how human beings work! Pro tip guys - you're almost certain to meet a woman at some point after you get married who, were you still single, you would have been interested in. Would I ever in any way consider being intimate (in any way) with them? Fuck no! I know some people desperately crave to rediscover the "butterflies" and the heart-skipping infatuation that they used to have with their partner, but it's a sign of serious emotional immaturity if you think that's all that love is. Love is so many things. Maybe my heart doesn't skip a beat when I see my wife like it used to, but she's my life partner and the only person I want to share my life with. When I'm with her I'm complete. I'm not going to throw that in the garbage because there's some woman at work who I click with!
It sounds to me like the woman OP got involved with really wanted to rediscover that feeling of infatuation, but never wanted to give up the partnership she had with her husband, and selfishly thought she could have both. If OP's story is honest, it sounds like she used him, he didn't have the emotional maturity to understand what was happening, and neither of them had enough integrity to know this relationship was wrong.
Look, if your relationship is bad and you need to bail, then bail. But don't try to bolt on a side piece. And don't settle for being the side piece either - first, you deserve better - second, the other partner deserves better as well.
This is me, except substitute "hotel room service" and "playing Magic the Gathering online in my underwear for hours at a time."