@boomerang,
Since you WILL be calling the doctor anyway, I'll go ahead and offer my reassurance... I've experienced that kind of thing before. It was when I was having an especially hard time as a teenager -- going deaf, etc. (Not physiological though, so far as I know, and while deaf = ear, I didn't have any typical inner ear problems like balance, etc.) I'd be sitting down and tell my body to get up and it just wouldn't. I'd get really mad at it, glaring at my immovable hands -- up, up! Then I'd suddenly actually get up, and feel normal after that.
I always associated it with depression, though I don't know for sure what it was about.