What is wrong with my knee?

I have many of these symptoms, although mine is from Ballet. I go regularly to physio, from this they said the muscle on my knee cap isn't strong and it causes my knee cap to slide around. so whenever i go to dancing (3 times a week) she taught me how to tape my knees which helps to reduce the swelling and pain. You may have done something minor and it hasn't healed properly, don't worry yourself the doctors will find out and it will get better. Sports are the main causes of injuries, keep your hopes up and give physio another chance, it may help.