Some of the possibilities that need evaluation in your case are anemia,fibromyalgia,chronic fatigue syndrome,hypothyroidism,depression,arthritis,chronic infections,diabetes and malignancies.
physical examination along with
investigations like complete blood count
and ESR blood
, platelet count,Rheumatoid factor, creatine kinase,electromyography and muscle biopsy and blood sugar levels may be needed to make a diagnosis.Pls consult a physician for that.
I hope that helps.