how do i know if i have a disease since, i get tired really easy, i feel down,tired un-energetic, i also get frequent headaches, loose of weight since im 16 and im 100lb i cant gain or loose weight at all!! and im moody most of the time, i dont get enough sleep since i go to bed at 12am and wake up at 5am for school. Am i sick or something? Doctors Cant diagnose if i am or not. HELP!!