What did I do to my knee? Really bad pain!?

You had a quack for a doctor. I sprain my acl it hurt like hell and i had to wear a long braces with a lot of straps, so you probably sprained it because if they gave you pills to keep inflammation ( white fluid in the knee ) from building then that's probably just a sprain, but just to be on the safe side go to a good doctor who knows what the hell he or she is doing and they'll tell you.