It could be this thread.
I am one of the invisibly disabled. I have a piece of paper somewhere that declares the percentage disabled I am, from a work injury long ago. I have a stupid genetic condition that makes my collagen broken, makes my ligaments loose (so my joints dislocate, all of them, at random), and provides me the joys of chronic pain. Sometimes I limp, and I walk slowly (and not far); but pretty much, you cannot see any of my disability when you look at me.
It has made for interesting times with partners. Most of my partners have been completely physically normal; FBF is not neurotypical, but strong and healthy. CBF is overweight, and has profound hearing loss (though it doesn't prevent him from carrying on as if he didn't)(it makes life fun).
They have a hard time understanding. When a normal person has an injury, they have pain, they take meds, they wait, they might do physical therapy; but they eventually get better. There is no getting better for what I have. There are good days and bad, and it's very difficult for people who don't have chronic pain to understand.
I've been in chronic pain for over 20 years, so I've quite learned how to manage myself and my interactions. I rarely take it personally when someone has a hard time with it; I know they can't understand.
I tell people early, because I don't see any point in hiding it. If you can't deal, I'd just as soon you go before I get attached. However, a lot of people don't understand what it means to deal, so they bravely say, 'I can handle it,' only to find out they can't. I get really pissed off when they're not honest enough, or able to say 'I thought I could, but I can't.' However, I do understand why that happens. Nobody wants to admit they don't want to be with you because of something you can't control.
And to end on a cheery note, sex makes endorphins, endorphins ease the pain. And I'm incredibly flexible.