question: Okay so recently when I stand up I get a rush of black spots like most people do, but whenever I try to shake it off my knees will starts to get weak. It feels as if my whole body is having a spasm, because my body moves back and forth. I have fallen to the floor when this happens, now I usually try to lay down and close my eyes and wait for it to pass. Could you tell me why my body is doing this?