Confused

Ok, today in school, I was talking with Lil Angel and messing around. I moved wrong, and I think I really hurt myself. But this certin...infliction...happens alot, so I never really thought it could mean anything. At least not until today.
What happened was my knee cap (?) popped out of place, I think. My Bio teacher says it could get really dangerous if I don't see a doctor, because this happens 3+ times a year, and I've pretty much gotten used to it.
But today was different than it usually was. The pain is lasting longer, and my leg feels REALLY tight. It still hurts to walk.
It's a little scary, mainly because it's been going on for so long...so does that mean that I could be in real danger?
I may be over reacting, but I'm not sure...