I'm a 16 year old girl, and for the past 3 days whenever i stand up, i get a pounding headache that matches my pulse in the back of my head, from my next to my ears. it feels like my head is in a vice or somthing, you know, like a lot of pressure on it. and they last for probobley 30 seconds at a time. their not very long, but they hurt very bad and i don't know why i have them. i took an advil but it didn't work at all, and i don't know what to do now. thank you :]