See if your son is anemic or suffering from hypoproteinemia
or stressed too much with his school work. You can also get his hormonal profile done along with a complete blood count
and urine analysis. He may need some nutritional supplements and relaxation exercises to tune to normal sleeping pattern. In case of any detected hormonal deficiency
, it needs to be corrected. Recent illnesses can also cause this problem. You should also get a complete evaluation as above and get proper treatment. Wish you good health.