Hi there!
I've read a few of the responses you've gotten & I've got to say that I'm fairly shocked at how many women out there really believe it's our 'job' as a wife to please our husbands whether we really want to or not.
My husband & I went through precisely what you're describing for a good long while when the kids were very small. I honestly believe that as women, we generally work harder than men. I'm not saying that men are lazy, I'm saying we have more people counting on us more often & we are only human also.
My husband had a hard time understanding that I worked just as many hours outside of the home as he did, earned half as much, and because I worked all day-work & he worked shift-work, once I came home I was on my own with 2 tiny kids as well. He would get home from work in the middle of the night which was 3 hours before I had to get up & expect to just jump into bed & get things going. Sorry, but no, especially not on a day where I hadn't even seen him all day & certainly hadn't been made to feel like anything more than a sleeping lump he wanted to have sex with.
I'm exagerating of course, but I'm willing to bet you get my drift. We sat down & had a long conversation after what felt like a never-ending time period where I wasn't feeling like a woman & he was feeling rejected & both of our feelings were hurt. We decided we needed to be there more for each other, him for me mentally & me for him physically & we needed to COMPROMISE, which does not mean I needed to start having sex with him every time the thought crossed his mind.
As the kids got a little older it became much easier to fit it in on weekend afternoons, early mornings, etc. but really once the kids didn't need me to do every single little thing for them I started to remember what it felt like to be Melissa & not just Super-Mom.