3 yrs ago my doctor diagnosed me with fibromyalgia. last week he said "... if there is such a thing." should i change doctors?

Have you been: pleased with care you have received to date? If yes, it might merit discussing with the doctor to clarify the meaning. That response/ interchange can help to guide your decision. Take care.

Yes: A doctor who expresses doubt whether fibromyalgia is "real" should refer suspected patients to a doctor who believes in this diagnosis. There are ways for patients to improve, but they need a doctor who understands the subtleties of the disorder.