Feeling constantly sick and tired.

I'm 17yrs old and I'm in my final year of high school- I don't stress really at all so I don't think it's stress related. I used to be sleep deprived a lot, as in maybe 4-5hrs (even less sometimes) every night. For the past two weeks in an attempt to better my grades and 'turn my life around' I've been trying to sleep regularly 8-10hrs a night and so far it has been working. I'm more tired than when I was sleeping less. I am constantly tired and find myself getting really sleeping at around about 5pm. I get these stomach pangs all the time I don't know how to describe what they feel like I suppose if it were possible for your stomach to literally chew itself up- that's what it feels like. I feel nauseous most of the time and end up vomiting. I have terrible aches in every part of my body and I am not extremely athletic although I exercise everyday and eat reasonably healthy.