FIBRO OR MCAS?

I recently diagnosed gwith fibromylgia but my first symptoms a have allergies all over my body then flu like synptoms then after my allergies like hives is gone my pain didnt gone a have a lot of bloodtest came back normal then my rheumatologist said fibromylgia ?? is this fibromylgia or mcas i recently noticed that i dont have a lot of pain but more on headache migrane.. im confused now because there is no diagnosing mcas and fibrod help with your comments thanks