What Causes Horrible Throbbing Pains On The Side Of The Head?

okay i have had horrible pains that last for a few minutes that start on the side of my head and throb. when these pains occur my vision almost completely blacks out. and i cant move for a few minutes. quite frequently my eyes jitter back and forth and i cant control it. like a tremor. now my right eye has begun to continuosly twitch. these pains can last for 3 to 30 minutes but i cant function when they occur. i usually fall to the ground and wait to regain my vision. This happens about 2-3 times a week.