A., I feel for you!
Remember that old advice: Wrap yourself in Saran Wrap and meet him at the door! JUST TEASING. I wonder how the Saran Wrap company felt about that kind of free advertising!
Anyway, we're significantly older than you, but we suffer from some of the same. I'll start by saying that I haven't "let myself go" and we are still very attracted to each other - so that rules out physical avoidance. In our case, it is tiredness that effects sex drive. We get up at 6 to get the older one on the bus for middle school and don't stop until around 11 p.m. By the end of the day, after working all day, being taxi and chauffer, chasing three kids around the homework tree and straightening stuff up a little, he's exhausted. We both are, actually, but it's only his drive that seems to be effected! All he wants to do is collapse in front of a TV and veg out. By the time he winds down, it's often really late and he's too tired.
At some level, I think this is a performance issue. TV is a means of avoidance as well as a means of vegging out. I think a lot of men feel that making sure their wives are satisfied is a performance issue, and if they're pooped, then they don't have it in them to "perform."
It's funny, for me, I'd be happy with some snuggling and a quickie if one of us is tired. I don't necessarily need a lot of "performance" on a nightly basis! I'm working on getting that across to him.
Here is something a friend recommended to me a couple of days ago. I am going to try it:
Tell him, "let's NOT have sex for a week, but let's just snuggle and kiss without making love." She said that it might take the pressure off of him to make love, and increase his willingness just to snuggle, etc. She hypothesizes that by the end of the week, he'll (well, we'll both) be so ready that it will jump start our sex life all over again. It might be worth a try!
Good luck and I'll be watching to see what kinds of answers you get.