Knee pain... possibilities on what it could be please?

ok im 15 an a girl an i weigh about 217 im a varsity softball starter an im having knee pain an have been for years. I am starting to get really concerned because on the right ride of my knee cap almost under it there is a sharp pain an on the right ride of my knee, like the side of my leg, is a little swollen all the time an i can only feel it faintly when i touch it or like scratch it. This numb like feeling is starting to go down my calf. Also when i walk it pops really loud an when it pops it hurts. This knee problem is making softball pretty hard an id appreciate any help i can get.....an yes i plan on going to the doctor soon