headaches and exhaustion

I'm a fifteen year old girl, and since march i've been getting terrible headaches, usually on the right side around the temple, sometimes on the left side. I felt better for a little while during the summer, but the past few weeks it's gotten worse and worse. Lately i've been feeling a little sick to my stomach. I've been exhausted and sleeping a lot. I missed a quarter of the school year last year and now my grades are suffering because I fall asleep in class(seriously, I wake up and have no clue what we're doing, no matter how hard I try!) anyway, i've had two mri's and they found a microadenoma on my pituitary gland, but the neroligist said that definately wasn't the problem. I've also been told it could be migranes, a complecation from a virus, and a pinched nerve, but the medication, chiropracty, and sleep hasn't helped. I've kept a calender of what I eat, when I sleep, and when the headaches happen(usually lasting between ten minutes and an hour or two), but I can't find any pattern. If anyone has heard of this type of thing before, or if you have any suggestions of what I should do, please tell me! Thanks