Hello, I Am 14 Years Old. Probably About Since December

hello, i am 14 years old. probably about since december maybe even november my legs have been constantly hurting (burning/stinging feeling) from my hips to my knees. it's got to the point where i cannot participate in gym class. (i cannot climb stairs well just moving and not moving my legs hurt in general.) i also get very dizzy and tired easily, i fall a lot. do you have any idea what this could be or point me in a direction?