You are living through one of my personal worries: dental work gone wrong on a grand scale.
Have you gone to a prosthodontist for a consult? I'm not saying you need false teeth or anything, but maybe they'd be able to fix your bite more accurately than anyone so far. (??)
I've had the type of pain you are describing on occasion, but not for any drawn out length of time (that is to say, not on an ongoing basis.) Just came to assume it was from bruxism. Maybe this is what your dentist meant? Still, if you are in pain, I'd be hesitant to stick with a dentist who laughed at your concerns. Within the current practice I go to, I actually switched dentists for a similar reason. It was a little awkward at first, but now it's fine.