Sad, I do relate to what you're saying, though I was already married a few years before my fibro really became an issue - and my husband has stuck by me through it all, not that he always REALLY gets it. But he believes me, at least - that took some work. And I know he loves me.
However, I haven't been so lucky with other people. I've lost some of my oldest and dearest friends and relatives, and all I can think of is that they just don't "get" me. I don't feel like I go on and on about my problems; in fact, I'm a great listener and commiserator. Maybe I forget what they tell me, and they're offended when I don't remember something? Maybe I'm a downer because I can't keep up with them? Whatever it is, it hurts a lot. Even my son thinks this all originated in my head and my head has to get me out of it .
All you can do is be yourself. Try to be positive, I guess that goes without saying, but what else can you do?