Why hasnt my period started?

Ok im 13 almost 14 and i havent started my period yet and my mom stated hers at 12 im getting worried because its bin hurting down there for about 11 months almost a year and my mom thought it was a bladder infection but its not i got meds but it didnt help. Drinking alot of water seems to help but i really want it to stop. But i think thats why i dont have my period im so worried. Can some one help me?