I remember a really sad article I once read by a guy who wrote about the end of his marriage. In the last months, he felt that his wife had decided that she should have sex with him not less than once a month (or something like that) and he could feel when she was deciding it was 'time' and 'giving him what he wanted'. She would watch anything on telly rather than spend time with him; he felt rejected for the cast of dodgy TV movies from 1988. He wrote about the pain of loneliness so well.
Having said that, yes, once or twice a week for a couple with 2 children under five sounds, i'm afraid, a pretty hot schedule from my perspective!
We tried doing that 'sex every day' thing that some woman was all over the papers advocating a couple of years ago. In fact, we tried it two separate times, and each time got to 4 days and I went on strike... not very honestly, I just refused to go to bed. The idea of it was to remove the decision-making pressure of it - the low libido partner becomes the decisionmaker/gatekeeper and that does feel like yet another responsibility on top of the children. The brutal truth for me is that sex does not mean orgasms (at the moment, for either of us), and good, pleasurable sex is random - sometimes it happens, sometimes having sex is not pleasurable enough to be distracting, and I have to spend the whole time fighting off all the unpleasant thoughts and worries in my mind. Telly or a book is a reliable distraction, I know if I am watching telly or reading I won't have to think. Sex requires me to think and pay attention, and when it is bad or boring, the thoughts get darker and darker - i feel less and less worthwhile, and start chasing good feelings, sometimes by doing stuff I'd rather not do, and sometimes by getting intensely angry,which makes me even more miserable and I end up finishing pretty abruptly and then feeling even worse. DH of course knows and loves me, and wants loving intimacy rather than any kind of sacrificial sex, so e.g. giving him a BJ when I don't really want to but want to do something less intimate than intercourse, is not satisfying to him.
Well, this is a muse rather than a helpful post. But I think for the lower libidoed partner, it gets more and more complicated, and surrounded with more and more issues, whereas for the high libidoed, it gets simpler; sex feels wonderful, it is the most intimate and private thing you can do with your beloved, we're both tired and fed up, it would make us feel better, why aren't we doing it now??
I don't really know the answer. I do agree that to say 'it's your problem' is not helpful. I would also counsel hope in that you really are in a tough place age-of-children wise, and that things are very likely to improve.