I second, or third, or nth, the advice to go see a doctor. Specifically, I would suggest an orthopedist who takes care of your nearest professional sports team, big time university athletic program, or ballet. This organizations will have the best and his (a knee specialist is most likely to be male) patients will not be happy with a suggestion to discontinue their activity. He will be of a mindset to help you continue your sport.
Good luck, and keep us posted.