Knee problems at 14? help me please?

Okay I'm 14 and I'm very athletic my knees been hurting me. Its a pain that comes and goes but when i have it it really hurts and i was doing hurdles and i hurt my knee it would hurt in practice but i never told my coaches till i hurt it more it still hurts very bad and i tell my Mom and she says its growing pains but its like a sharp shoting part. Through my knee cap. Please help me. I want my knee to stop hurting please help me!