By Anne Fisher, contributor

Dear Annie: I have an unusual problem, but I hope you and your readers can give me some pointers. The situation is this: I suffer from fibromyalgia, which occasionally (about twice a month, on average) is so painful that I literally can’t move.

I’m taking medication for it, so it’s much better than it used to be, but it is unpredictable. In my last job, I managed to work around it, but now I’m unemployed and seeking a new position. I want to be totally honest with job interviewers, but I’m afraid that, in this shaky job market, if I tell them I have this condition, they won’t hire me.

I know employers are prohibited by law from asking candidates about medical issues, but should I bring this up anyway? If so, when is the best time to mention it? –Just Jo

Dear J.J.: Your situation is not as unusual as you may think. About 20% of the population has a disability of some kind, the Census Bureau reports. Of those with conditions categorized as “non-severe”, 48% between the ages of 21 and 64 are working full-time, versus 63% without any disability who hold full-time jobs.

The gap is smaller than you might expect, given that most employers — 82%, according to a survey last month by the nonprofit Kessler Foundation — have no programs in place for integrating people with disabilities into the workforce.

Moreover, the poll found that 19% of companies have a specific person or department overseeing the hiring of the disabled. That’s a big drop from the 40% rate that was recorded the last time the foundation surveyed employers on this question, in 1995.

It may not be coincidental that the Equal Opportunity Employment Commission says more people with disabilities filed discrimination charges against employers in 2009 than at any other time in the federal Americans with Disabilities Act’s 20-year history. About 21,500 ADA-related complaints were filed with the agency last year.

The issue becomes especially complicated with a disability like yours, which is often called a “hidden” or “invisible” one.

As you mention, the ADA prohibits hiring managers from asking job candidates any medical questions, and the consensus among legal experts in this field is that you’re under no obligation to bring up the subject in an interview, unless you have reason to believe it could affect your ability to do your job.

And there’s the rub. Since you managed to work around your condition in your last job, do you think you could do the same in a new position?

Or do you have reason to believe it will be harder this time around (for example, if the illness has gotten more severe, or the episodes more frequent)?

“You need to do a candid self-assessment,” says Lori Golden, head of an extensive program at Ernst & Young called AccessAbilities, aimed at hiring and developing talented people who happen to have disabilities. “How often do the episodes of severe illness occur and, most important, what is their impact?

“The Americans with Disabilities Act requires employers to make a ‘reasonable accommodation’ for people with disabilities,” Golden says. “But if you really believe you could not perform at a high level even if the employer is willing to work with you on it, then don’t apply for that job.”

Of course, making this determination requires that you understand exactly what the job will entail, so ask interviewers for as much detail as they can give you. Then, figure out what kinds of “reasonable accommodations” might be possible.

If, for instance, it would help to be able to work from home occasionally, you can ask about that in an interview without going into detail about why you want to know.

“Flexibility about when and where you work is one of the most important tools for people with disabilities, so seek out employers who offer that,” Golden suggests.

The main emphasis of your job search should be “your skills and experience, and why you would be a great fit,” she says. “Focus on your abilities, not your disability.”

Once you are hired, consider having a candid talk with your new boss about your condition.

“People tend to overlook the risks in not revealing the information. Bosses can’t make a ‘reasonable accommodation’ if they don’t know you need one. If you do get hired and your performance falters because of an illness you’ve kept secret, it can be hard to repair the damage,” says Golden.

To help both employees and employers navigate this complex territory, Ernst & Young has written a free online guidebook called “Getting support, supporting others.”

Among many other issues, the guide covers career development for people with disabilities.

“Getting hired is great, but then what?” asks Golden. “At Ernst & Young we really focus, not just on hiring and accommodations and so on, but on building a great career path.” Smart.

Talkback: Have you found work despite an “invisible” disability? Did you mention it in interviews, or after you were hired? Leave a comment below.