Bad knee pain in my right knee after I run or jump...?

So for about a week now, I've been having pain in my right knee after I exercise. After I jump (even on my trampoline), run, and sometimes walking at a fast pace, my knee-cap starts aching really bad and I feel like I need to sit down and elevate it on a pillow. :( I'm only 13 years young and I don't have a clue what's wrong with my knee, but I do naturally have "knobby" or "bony" knees. I inherited it from my mother. Could my knee be sensitive because I don't have much tissue and fat on my knee cap?? Help me and answer if you might know what's going on. (I'm also a cheerleader and when I'm doing stunts and dancing, I feel the need to sit down and stop cheering that moment...I don't want this to get in the way of my favorite sport.) :/