hi i am 16 years old, and for about 3 weeks now i have been feeling really tired and not wanna do anything anymore. I am extremely weak and light headed all the time, from the time i wake up till the time i go to bed. I get major headaches occasionally and they get pretty bad. Also, i sometimes get nausous but not all the time, I sometimes dont eat much and have hard time sleeping?? Its kind of scaring me... I dont know what to do? I need to see a doctor, but half the time, the doctor doesnt tell me much anything, and says that nothing is wrong... ???