If you are on the verge of losing your relationship (or what have you) don't reduce yourself to being used as an object. You're worth more.
More so when you are married and have no real desire to have any kind of sexual interaction regardless of age.
Compromising is one thing but if you have expressed countless times you don't wish to have sex, don't let them have you choose.
If they treat you unfairly, why put up with it? Just break up, get a divorce or something. You're worth more than you know.
Realize that you are way more worthy than a quick fuck.

Just some thoughts about this in general.