Thanks for posting your query. The tests you have done are normal. Have you got your thyroid
hormone level tested? If no, please get it done, as this might be one of the causes.
One other cause is Chronic Fatigue Syndrome
(CFS). The treatment for this is symptomatic and behavioral. Please speak to your doctor about this.
Sleep- relaxation techniques
, and massages will help you.
I hope this helps you. Get yourself evaluated by your doctor.
I wish you good health.