You are right that fybromalagia is hard to test for. It's basically a diagnosis of exclusion and some doctors still think that it's a lazy diagnosis--not that it doesn't exist, but that it's poorly defined, even more poorly understood, and therefore, treatments are few and far between. A doctor can label someone with it and then say "well, not much we can do, try these pills."
As for your pain, Ioka, sometimes regular narcotics don't work well if it's nerve pain. Anti-seizure medications work better. Of course, I don't know if nerve pain is what you have, but if it is, that may be why even the morphine doesn't help. Just a thought.
Have you been to a neurologist?