If I don't feel up to an appointment/engagement/activity, I just tell the truth, but keep details out unless asked. So I say, "Sorry, not feeling very well, can't make it." I figured it shld matter nothing to me if the person thinks I'm an anti-social, boring person, as long as I know I had good, valid reasons for escaping (like how you have gd, valid reasons to skip an appt to attend to a sick child. Except in this case, you're attending to a sick adult).
If the person knows abt my condition (e.g. I have mentioned it to her before in the spirit of sharing), I might go: "Having fibro pains, darn, can't make it."
With my family, I'm more myself, but I don't see my parents often enough to become a real nuisance (not in same household). My husband, well, he's the long-suffering one. When my feet or hands hurt, I'd tell him, and sometimes try to get a foot/hand massage by whining (actually, I ask directly: "Can I have a foot message?"). He usually complies. My trick is to ask for it while he's semi-busy, like when we're watching TV, then massaging becomes less of a chore and more of a minor inconvenience - and cld even be subconsciously deemed an act of devotion! Actually, truth is, when you're concentrating on something else (the plot of a movie), you don't realise you're working part-time. It's like how you can eat bags of popcorn and wonder where the food went when the show's over.
But seriously, to my boss, I tell the truth, though in vague terms, and I've always taken pains to give the impression that I'm trying my best to get better (which is true). Ever since getting treatment, I've been doing much better, so tt helps, too.
Yes, scbagrrrl, sometimes, we really need someone who'd really understand to listen to us whine. But it's tough, since the fibropack is a diverse lot themselves. And where I come from, I seem to be the only one inflicted with these strange bodily reactions. And I often suspect I don't have FM but somethng else the doctors failed to pick up.
Hmmm, if you feel down, and am not sure what to say to others, take a nap, if you can. Then you may feel better and the problem may just become a non-issue (with some luck) or, you may be more decisive abt your next move. Problem is we only get this luxury on a weekend (for those still well enough to work). Gd luck!