OP, I have heard that fibromyalgia can be very painful. I understand how this may put you off from sex if every time your partner comes near you, it's going to give you pain. You've been together for 28 years, may be you can explore some other ways of enjoying physical intimacy together, if he doesn't want to shave his body hair for you. Which again, is something he and you should definitely sit down and have a honest conversation about.
Just something to keep in mind - there are other ways to have satisfying physical intimacy with a partner. Like toys, words... even a look of appreciation. Sometimes I don't feel like having sex, I might be on my periods and I don't like messy sex, so I just give a BJ to my hubby, it still counts as sex to me as I can make sure I get pleasure from it. I do this because I still find him attractive and desirable, in spite of the fact that he has a prickly beard that I certainly don't admire.
I shave my pits, and so does my husband, because neither of us like hair in our mouths. There's mutual consent here. He has a designer stubble that's very prickly - ouch! - so we kiss carefully. It slows down things, yes, but I don't mind it, really, I like careful kisses. And obviously we do other things too! Personally I can never say no to sex fully just because of a beard. I don't think I will like it at all if my husband refuses to have sex with me unless I "did something" for him.
If you are saying no to the whole concept of sex itself because your husband refuses to share his beard, then there seems to be more than just facial hair to this discord.