WITL Unfortunately, what has happened is that you have got sucked back into both his and society's script about why men have affairs. I really want you to try and step back for a moment and look at this logically. I also want you to bear in mind that your H, like a lot of emotionally immature adults in shock, has retreated to child mode. When caught red-handed doing something that can be no-one else's fault, there is an instinct to hurl the "You made me do it" defence. If he was a child you wouldn't accept the blame and you'd tell him to take responsibility for his actions.
His anger is less to do with being neglected and more about being found out actually. He is literally furious with you for rumbling him and the more indignant he feels about that and having to accept he was in the wrong here, the more he is going to counter-attack with "reasons" for why he behaved as he did.
Most married adults know that infidelity is wrong and unfair, but because the weakest cannot take responsibility for doing a bad thing, they have to find just cause. Unfortunately, society colludes with this and the sexual politics influence people's choices, so that affairs are thought to be understandable if someone isn't "getting" something from their marriage.
Well actually that needs unpicking because what you will find is that this affair didn't happen because your H wasn't getting enough, it happened because he wasn't giving enough.
You've got 3 children of 5 and under by the sounds of things, which is more demanding of your physical and emotional labour over 24 hours than any full-time job. But it sounds as though you have been doing this pretty much single-handed while your H has worked, enjoyed corporate entertainment and gone to parties. Lots of working parents find young children exhausting and after a hard day's work, want to come home and switch off. But they can't - they have to be in Daddy or Mummy mode as soon as they step in the door and share the load with the partner who has been tending to their needs all day. Their sense of fairness kicks in and they realise that their partner needs a break. Selfish and immature parents however, stay out late after work to avoid all this, tell lies to their partner about where they are and only return when the kids are bathed and in bed.
By that time, I expect you felt anything but sexy, desirable and adoring of your H. I expect you just felt exhausted.
I want you to reverse the sexes here and imagine your H had been the primary carer and you had been the breadwinner. Imagine yourself behaving exactly as your H has since having DCs and then tell me who you think has been giving more to the relationship.
I also want you to stop thinking about what your H hasn't been getting and focus for a moment on what you haven't been getting from your romantic relationship. Have you felt nurtured, understood, adored, desired intensely, loved and cared for, listened to, supported, given a well-deserved break, treated, able to discuss and realise your aspirations in life?
If the answer to that is "no" and you still wouldn't have had an affair, then see this defence for the absolute sham it is.
The truth of affairs is often rather more mundane and a lot less complex that people involved in them would have you believe. They never happen in a vacuum and are usually an extension of behaviour that was already there.
Therefore, affairs often happen just because an opportunity arises for a romantic and sexual adventure and a person says "Why not?"
And it's as banal and simple as that.