Headache, Late Period, Stomach Growling?

I'm 13 and have has my period since December 09. I'm obviously a virgin so I can't be pregnant. My period is about a week late. I've been getting a slight headache lately. I feel drowsy and/or tired all the time. I may just be stressed because of finals. As for diet changes, I've started drinking milk for the first time again in a year. Help pls.