Im 12 and my knees have been hurting for over 3 months ?

im a cheerleader, dancer + gymnast. my mum thinks im experiancing growing pains in my knees buh i dont think growing pains can last for nearly 4 months NON STOP. they hurt when i run, skip, bend down then stand up, going up stairs crossing my legs. my question is CAN GROWING PAINS LAST FOR 4 MONTHS.? + CAN ANYONE DIAGNOSE MY KNEE PAIN.? thanks(: