Disclosure Decision

Ever since the beginning of my struggles with pain in my hands, I have also struggled with the challenge of deciding when to tell other people about it. When is the right time to disclose that information? How much is appropriate to tell?
I've tried to tell people as little as possible and as infrequently as possible. I've never wanted to be an object of pity. It's never been easy for me to say that I cannot do something, or even to ask for help. There is an enormous emotional hurdle to overcome by admitting to others, as well as myself, that there are things I simply should not do.
I tell my students about my condition in the first couple days of class. They need to know right away, because they will soon be asking me for written bathroom passes. They also need to know more about the condition, because invariably they ask questions. They want to know more. It's best to explain it once at the beginning of the semester, rather than 36 times at inopportune moments throughout the rest of the semester.
I usually tell coworkers only on a need to know basis. I'm working hard to prove myself in a new career, in a new school, with new people, and I do not want to be seen as someone who complains. If I start the conversation by saying that my hands hurt, most people over 30 will respond in kind with what they perceive to be a comparative pain of their own.
"My hands hurt..."
"Oh, I know how that is. I've been grading papers for the last couple of hours."
Perhaps I should start the conversation by expressing what I need from them.
"Can you fill this form out for me? I can't write."
This seems to raise more questions, and casts some doubt on to my credibility. I don't look disabled. Who would believe it?
Sometimes I wear a glove to remind me not to use my hands. This is usually in the classroom, where my students already understand its purpose. I've even trained them to remind me to wear the glove when I am talking with my hands too much.
There is a drawback, however, when someone who does not know my condition sees the glove. Usually they make some comic reference to a "Michael Jackson tribute" and I will laugh it off. It usually does not seem like the time or the place for an in-depth explanation of a medical condition.
If I had no arms, no explanation would be necessary. The same would be true if I walked with a limp, or used a wheelchair. They would come to some "obvious" conclusion about my abilities based on their observation.
If someone asks me to hold something or let something or write something down, I find myself in an awkward situation. How can I appear helpful as I decline to help them? An explanation of my personal struggles seems inappropriate at the moment.
Sometimes I send out a form letter e-mail with a brief description of the condition and a link to this blog. There is no way they could understand my struggle to maintain a balance between credibility and sympathy.
90% of the people in my world have the opportunity to be oblivious to my condition. That includes students, friends and family who already know about it. They don't need a full explanation each time, but a reminder is often necessary. I find other ways of doing things so that we can all forget the obstacles and focus on the achievements.

I don't have the answer here. I don't know exactly how much to say and when. I wish I did.