According to the symptoms you report (fatigue, muscle pain, muscle weakness…), you might be experiencing myalgic encephalomyelitis (ME). Another term for ME is chronic fatigue syndrome (CFS). ME or CFS has an unknown etiology but it is believed that it is caused by a virus or inadequate immune response to the viral infection. Symptoms (fatigue) last more than 6 months before diagnosis. But before establishing the diagnosis for ME or CFS, several other conditions that can also cause chronic fatigue must first be excluded: infections; autoimmune diseases; tumors; some neurological diseases; endocrine diseases like hypothyroidism; psychiatric disorders such as depression; drug dependence, and other illnesses (such as heart, kidney, liver diseases). One of the neurological diseases to be excluded is multiple sclerosis (MS). You can request a CT-scan or a MRI to investigate possible brain changes typical during MS. If there are such brain changes, you should then perform a laboratory analysis of the cerebral-spinal liquid. You can ask for expert help from a neurologist.