narcolepsy
"I fall between fatigue and narcolepsy.  Things like falling aslleep at traffic lights, work and at home.  The doctor thought it might be the side effect of sleep apnea, so I took the test and ended up very low (6x per hour).  I was put on Provigil which I soon fell asleep on, then on to Nuvigil, which wasn't strong enough.  Ritalin was next but it gave a big crash when it ebbed.  Now I am on dextroamphetamine and it is helping immensley.  No more falling asleep in the car or at work and at home (which was putting a strain on my marrage.)"