i go to bed at 9 at night. i wake up at 7:15. i'm always tired when i wake up and tired for the rest of the day. it really affects my grades and my attitude on everything. i get really cranky and want to sleep more. i get like 9-10 hours of sleep a night, and i'm still tired.

here's the funny thing. when i stay up late, like 12-2 am and i wake up at 7:15, i'm really refreshed and i feel a WHOLE lot better. why does this happen?

?????