I've been foolish

This sounds like infatuation and it sounds as though your lover is not into commitment. There is nothing to be achieved in telling your husband. It depends what you want in life but you could be left by your lover in the future. Would you be prepared to give up your present lifestyle and security?

I don’t know what AP means but apart from that I understand your post
It’s tough isn’t it they both have what you want one.. security, familiarity and a long faithful marriage through thick and thin and the other intimacy that you crave, excitement and the novelty of a green oasis after years in a desert Mix the two guys together and you have ‘the perfect man’
But there are a few red flags apart from the unfaithfulness
He is a complicated person who finds commitment and communication difficult, he does not have a good income
I wonder if he is about to break it off and various things lead me to believe this he also has no guilt about breaking up a long marriage!!!
It’s tempting though isn’t it ?
How would your husband react if he found out.. fire and brimstone and kick you out or realise you need more and accept (99% would be the first, a few men could accept the second)
I don’t think anyone can really help here you know far more about both men and obviously have huge question marks over the second guy although it’s wonderful at the moment.

Sorry there are no real answers at this stage you have to weigh it all up throw it in the air and see where it lands
A couple of things though can you imagine never seeing your husband again and has the other guy suggested you leave your marriage for him ???
(do you have children with the marriage? Could complicate things further)

I agree with Nanny. This man may just want a fling. It's a nice fantasy , but if in reality it ends up not working out or just simply fizzles, where would you be? Idk, adventure is nice but we have to live in the real world, and there sometimes we need survivial and comfort keep us safe and secure in a cruel cold world. At least you know someone else found you attractive, in case mb you thought the reason your husband wasn't interested was that you had become unattractive, boring or just not desirable. Clearly you still have it! That should be of some comfort. I wonder why your husband is so distant? It could be a psychological thing, especially in old age people get down or depressed in life. Or plain tired. And men's bodies, just like women's, can have problems that mb are embarrassing to talk about and can effect sexual desire. If you and your husband still have love and respect for each other, that's something to cherish too though. Sex is sex.....but love is what endures.

I'm sorry that you feel so unhappy having found yourself in a rotten situation. It most certainly isn't all your fault as your DH has inadvertently pushed you away.
Regarding AP, as I see it, he is in a safe situation knowing that you are married and this could possibly protect him from ever making any sort of commitment to you.
It could be that this is just a fling and won't go far anyway. Don't tell your DH about it as it won't achieve anything, it may relieve any guilt you may have but it won't do him any good.
You need to think very seriously about what you want and I wouldn't be tempted to give up a good lifestyle unless you can't actually stand living with DH any longer.
If you have the strength to end the relationship with AP it may save you a lot of heartache longterm as by continuing it you will get deeper in. Above all, always remember that a certain things that happen are due to cause and reaction so please don't feel bad about it. I wish you well and hope that you can sort your thoughts out. xx