Fibromyalgia is a systemic disorder. It is a global pain syndrome generated by the nervous system.
Be aware that symptoms of musculoskeletal pain can be caused by medical conditions (autoimmune disorders), metabolic disorders (hypothyroidism, food allergies/sensitivities, nutrient deficiencies), mental conditions (post-traumatic stress disorder, depression, anxiety, and panic attacks).
Muscle symptoms are a frequent found in thyroid diseases. There are signiﬁcant similarities between noninﬂammatory joint diseases and symptoms of thyroid dysfunction. Fibromyalgia patients have some problems in the production or utilization of thyroid hormones. There is an association between thyroid autoimmunity and fibromyalgia.
Recent study shows that fibromyalgia patients with a normally functioning thyroid gland had a signiﬁcantly higher prevalence of positive TPO antibodies. Thyroid autoimmunity is an important predictor of endothelial function and arterial stiffness in postmenopausal women with fibromyalgia and a normally functioning thyroid gland.
Please, have in mind that what is called normal is not necessary optimal. And normal is based on 95 % percentile. And you need to be at least at the middle of the normal range.
Ask your physician to take full thyroid test: TSH, total T4, free T3, free T4, thyroid antibodies (TPO and TgAb).