Every time I go from laying to standing, I get a SEVERE shooting pain that throbs in the right hand side on the back of my head. It pounds for a good 20 seconds, getting slightly less painful the more seconds pass. It hurts so much I can't do anything but stand and hold my head until it passes. Now this morning it started happening when I went from sitting to standing too, not just laying. It's also happening if I'm looking down at something and then change my direction to look up.

This doesn't always happen. It happens probably for about 3-4 days straight then stops, and it comes back again usually a few weeks later.

I'm not doing anything different. I'm very hydrated and drink a lot of water every day, I take vitamins, and I eat healthy.

What could be the reason for this?