I feel sorry for you OP, and understand why you are upset, except for you wanting to have an affair. Even if you're not having sex, you are married, you have promised to be faithful. An affair won't fix your marriage.
But I can appreciate it's hard for you and I think many posters here are unnecessarily nasty to you. Apart from the affair bit you sound like a very nice man and the attention you try to pay your wife and the favours you do and love you show her are a really nice thing and it is such a pity this isn't being reiprocated. It is soul-destroying to feel unloved and unappreciated in a marriage. And I don't think the things you do for your wife necessarily sound pressurising. What are you supposed to do, just leave her alone and live like flatmates?
I say all this because I am much like your wife at the moment, to the point that I actually wondered if you are my DH (though I don't think so!) :) I have a lovely, kind, loving DH who shows me love, gives me affection, does a lot of housework, cooks almost always, does a lot of the childcare when he's at home (he works, I'm at home) and whom I love very much. BUT we don't have much sex. I put it down to having two small DDs (2.5 years and 9 months) and still breastfeeding which I think may be suppressing my sex drive a bit. My DH would like to have more sex and I agree it would be good but by the time the girls are in bed all I mostly want is to be in peace and read or MN
And I'm incredibly lazy.
We would both like to kiss and cuddle more but the girls always end up getting most of the kisses and cuddles. And the sex...I don't think it's a good idea just to give up and live like flatmates. It won't work. But an affair won't either. It's difficult, especially if she really doesn't want to show any affection or share intimacy. But have you really had a proper conversation about this? Or could she be depressed?
I personally am determined to improve things and be more intimate with DH as I think it is very rewarding for both of us and an important part of any marriage - certainly not trivial as somebody said. I'm also hoping that when I stop BFing and go back to work things will improve.
OP - don't give up. Talk to her honestly about your feelings (apart from the affair bit). Good luck, I hope things work out for you.