Headaches??

 So it seems lately I have been getting wicked headaches.  At first I thought it was because I'm dehydrated, but now I'm not to sure.  I'm getting anywhere from 10-11 cups at day.  Any other suggestions that can be causing these headaches?  I wonder if it can be the Aspertame...

I always get headaches/migraines at the beginning of my cycle.  I think its my hormones all out of wack, is it just at a certain point in the month or is it consistent?