I expect your GP has conducted all the tests wildrose to come to the diagnosis that he has.
However, I would just like to say that a friend was crying with the pains she was experiencing, diagnosed as osteo-arthritis, sciatica, neck and shoulder problems and taking painkillers and anti-inflammatories. She could not sleep, could not walk or get in and out of the car.
After quite some time she was no better and the GP did further blood tests and she was diagnosed with Polymyalgia rheumatica. The treatment is with steroids which she was reluctant to take, however, she did feel much better so the dose was reduced. It returned so she was put on a higher dose again but now they have been stopped altogether and she is fine. She was also prescribed an exercise regime when she got better which she does religiously, physio exercises, swimming, some walking.
It's just a thought and this may not be the problem at all but worth enquiring of your GP perhaps.