I don't think it's about once a cheat always a cheat BUT once you have shown the ability to lie to that extent then you cannot be trusted. Most people can tell white lies, but the level of lying involved, bare faced to a partner you once loved to cover up an affair is an extreme amount. That takes a certain type of person. You are both now that type so neither can be trusted. Fact. It doesn't mean one of you will cheat but shows you can carry out high levels of deceit.
Having affairs is wrong. Fact. Continuing to keep it secret is wrong.
It makes me laugh that posters jump to defend OP from receiving a bit of stick on a forum she entered willingly. It shows there is no real Karma as the poor families left behind have a much harder battle to face. So she has some stick on here, big deal, she was expecting it. She is "happy" where as I'm sure the kids and partners aren't.
I have a friend who was the OW. She is now in a relationship with the man. She admits that her affair had a lot to do with how she felt about herself. Not good enough. It was an escape. She said that now she is with someone who is level as they both had affairs, and so neither are better than the other morally. How sad I thought. She hasn't resolved her issues but they are not in the forefront of her mind, as she admits she is with someone who also wasn't good enough. I found that totally strange and very sad but at least she isn't trying to pretend it's OK. As it isn't. She has thought a lot about her actions and admits that once the new man was involved it tainted how she thought of her marriage. Twisting things to justify the cheating in her head and to others. She isn't happy deep down, but now admits she will not end this new relationship as then all the heartache caused to her H and kids would be for nothing. This was a deep conversation one night, but day to day she puts on her happy face and pretends it's all good. This is two years on.
Everyone makes mistakes, but affairs aren't one mistake, they are a consuming web of lies, mistake after mistake after mistake.
It is also not true that relationships would fall apart anyway if the OW/OM hadn't come along. All to often the relationships could be saved, but the OW/OM gives an escape route instead. This said, I am not saying that all relationships can be saved, but affairs ruin the possibility. They taint everything. If the relationship needs to be ended it should be done without seeing someone else. If you are meant to be with them you can hook up in future once who have sorted the end of the current relationship and the children etc. When you chose to have kids you are agreeing to put someone else before yourself. That means any relationships need to be worked on, and if they need to end, handled correctly. Affairs puts yourself above everyone else including the kids.
I find it very interesting that the OP discovered his EA. How nice of you to save the poor man from it.
Do the other partners involved seriously have no idea at all that there is someone else? Do they even know you exist maybe as a "friend" but not know the full extent of the affair? They must have wondered I would have thought, it is a common question when relationships end...is there someone else?