You might want to look at this
https://www.caa.co.uk/Aeromedical-Ex...e-material-GM/
With the main paragraph that jumps out for Claass 1 medical as this 'Class 1 and 2 (a) An applicant with any significant sequela from disease, injury or congenital abnormality affecting the bones, joints, muscles or tendons with or without surgery requires full evaluation prior to a fit assessment.'
Many of the medications that can be used in FM can be disqualifying by themselves.
Probably best to actually discuss with an AME your particular situation and get appropriate medical reports from your GP/Doctor
https://www.caa.co.uk/WorkArea/Downl...?id=4294973698