I usually just tell my husband how I feel. I felt like this last weekend. I'm pregnant and horny all the dang time right now, which is not usual for me. He's got a particularly high sex drive but he also has a one-track mind. So, if he's over-involved at work or is tired, he's not interested. He's been quite involved with his job lately so we hadn't had sex in a while. This past weekend I finally told him I was feeling unwanted and I needed to feel desired by him. He felt terrible for making me feel that way and we had so much sex last weekend.... so I'd say that worked, LOL.
Have you tried talking to him about this? Figuring out what might be bugging him? If nothing else, get him checked out at the doctor. My Dad had low testosterone and that really affected his sex drive (lol, we have a very open family). He got a prescription and he was back to his normal horny self.
Good luck to you, I know how you are feeling, it sucks as a woman to feel un-desired. One of life's great pleasures, for me, is knowing that my man wants to rip my clothes off of me at any given moment. :)