An interesting article from an unlikely source:
. . . Fibromyalgia is considered a "made up" syndrome by some, but it's been described in medical literature since the 1700s. And if you've ever met someone who has it, you'll immediately realize that this is not something people invent to get attention.
. . .
As you might expect, being in pain all the time is exhausting. It has a debilitating effect on the libido, as do pain medications. Chronic pain often causes depression, frustration and anger, which adds strain to the relationship on a number of levels, including sex. And while sex helps with relaxation, it's hard to drum up desire when you're already stressed and tired.
Even if a partner wants to engage physically, an extremely sensitive neurological system can inhibit the pleasure response. A touch that feels ticklish or mildly tender on most people might be excruciating to a person with fibromyalgia.
So how do you have sex?
A graphic and useful article, it goes on to disuss various approaces and interventions, including technological ones. There is also an interesting conversation thread.