S., you've described me to a T. I have kids 6, 4 & 2, married 7 years, and I'm at the same weight as B.C. (before children). But I don't care about sex, even with a handsome, buff husband (he works out = high libido). Crazy me!!!
Talking about it with your husband is the key to keeping things together. Please do bring it up with him during a neutral moment so he understands you're still attracted to him, your body just isn't responding.
Next talk to your GYN - if you take certain medications they can decrease your sex drive for sure. That includes some birth control and antidepressants. Also do the hormone check as others suggested. Even if you go the homeopathic route, getting those hormones in line can do wonders for your well-being.
Do NOT "just do it" for him - you will end up feeling resentful and hate sex. It should never be a duty or chore. Believe me, I've been there. Don't kid yourself and disservice both you and him. Talk about it and work it out.
What I am trying is (1) regular exercise [hey it works for him] and (2) watching the timing. We all have the "good" days, we just need to be aware of them. And yes, it may be only once or twice a month. But, hearing my hubby talk about his workplace buddies' complaints, we are not the only ones!!!
Hang in there :)