Hollie
Everything you've said SCREAMS to me that you haven't worked hard enough to save your marriage yet.
It truly is starting to sound like it's dawning on you that you want to try.
I don't think you should walk away without trying!
When DH and I hit a similar point a few years ago (no affairs but some equally difficult shit going on) that is what I thought - ok, my marriage may not be what I want, but I haven't tried everything I can yet to save it. I owe it to DH, the DCs and myself to try my damndest to fix it and find my happiness within my family. Then if I'm still unhappy, I will know that I did everything in my power to try and fix things, but it just didn't work out, and then I would be able to leave with a clear understanding that I was doing it for the right reasons. A clear conscience.
We worked bloody hard, counselling, forcing ourselves to be more physical, starting with things like cuddles and massages and working our way up to sex, definitely going on more "date nights" (really hate that term), finding small ways to be kind to each other, talking more (our counsellor even had us on a script "Tell me 3 best things and 3 worst things about your day") and so on.
Now no marriage is "perfect" but we are happy. And content. We are real partners now, us against the world.
Don't tell your DH about the affair. That is just unfair - hurting him just so you can have the luxury of "being forgiven" (BIG IF) and a "clear conscience". I am afraid the guilt and the fear and self-loathing are your crosses to bear for acting this way in the first place.
Good luck.