It's very likely that she doesn't realise what sex with her means to you - that it's a prime way for you to feel close to her and to bond with her, and that her not wanting you makes you feel really low. As women, we can bond as well through talking, and she might just assume that sex for you means getting your leg over.
You HAVE to communicate what the lack of sex is doing to you. I have been in a sexless marriage and it was so much worse than I'd ever have thought it could be. I didn't think of myself as being especially into sex, but when my own spouse didn't want me for months on end, I have never felt so bleak and miserable and insignificant. It's actually quite unfair for someone to take you off the market and then refuse you sex. But it's about soooo much more than the act. It's about feeling loved, wanted, special, desired, all the things.
It's on YOU to sit her down and talk to her frankly and calmly about this. You absolutely must get through to her that sex WITH HER means a lot to you, and how sad you are without it. And make it clear that sex is off the table for the moment, so she doesn't feel pressured. And you want her to want it, anyway. You don't want a pity shag.
The book MATING IN CAPTIVITY might help. Some women interviewed for the book felt that marriage had legitimised sex so much that all the eroticness of it had disappeared. One woman talks about about how, after marriage, sex isn't as mentally arousing for her because she was now officially his only option.
The other thing worth knowing is that men's drives tend to be spontaneous whereas women's are reactive. So she won't spontaneously want it like you do, now that the early days are past. For me, scheduling sex tends to work, as then I have some time to look forward to it and get turned on thinking about it.
Check that you're not doing things like belching or have any other offputting habits, and be honest with yourself about if you do enough domestically.
But I think a lot of these problems can stem from the fact that our desire is largely reactive, not spontaneous. So unless you plan it, "it" never happens.
Try cuddling with no expectation of sex, and then touching sensitive parts of her skin, like running your hands through her hair, kissing her neck, etc. That's the kind of touch that can get us going, especially if we think he's just really enjoying touching us and not treating it as a short stop on the way to Legover Land.