What Causes Burning Pain In Head While Standing?

Hi I'm 20 years I'm around 9 stone and 5ft 2 so average weight for my size and have good health but when ever I stand up I get a burning pain in the side of my head and it doesn't go away. I thought it was because I wasn't drinking enough but it doesn't seem to be the problem! Is there another cause for this? Can u help please Emma k.