Sleep apnea, a thyroid problem, the melatonin you are taking is too high a dose, diabetes.... There could be any number of reasons. You should ask your doctor.
Eat right, blood sugar balance. Nutrition and exercise are key to energy levels.
Melatonin can also be ******* with you, also - endocrine disruptors.
I hate to break it to ya, but that's incredibly normal. You say that you wake up at 8 or 9 so to be tired by 6.. that's 10 hours.
could be your diet....maybe your depressed....myb low on vitamins like iron and b12...myb you should start exercising if you dont it may give you a boost..etc
Thyroid issues? Low iron?
take iron pills