Just to offer a different perspective...
It's not saying very much good about your husband (is it?) if you think that you're so undesirable no one would want you but him? If you're really that awful, why has he stuck with you for three kids and a mortgage and been at your side through your health challenges?
He could have left at any time, yes? But he didn't. He chose to stay. He could have sneaked off and found some younger hotter chickie into BDSM, but he didn't do that either. He asked. My guess is that he asked because he loves you, all of you, your insecurities and your challenges and all your wonderfulness, too.
Love is that condition in which the happiness of another person is essential to your own...
Robert A. Heinlein
Me: female, bi, (formerly hinge of a vee)
with FirstBoyFriend (FBF)(moderately long-distance)
and no longer with CurrentBoyFriend (CBF)(who now lives in a house far away-with stairs I can't climb)