Why Does My Head Hurt And Start Throbbing Whenever I

Why does my head hurt and start throbbing whenever I stand or sit up? Today is the first day it started and pain medications are not helping. It's fine when I lay down but the second I sit up it starts again. There is also a ringing in my ears. I've had headaches before but nothing like this. The pain is probably an 7 or 8 out of 10.