GIRLS ONLY!! Period Problems??

K. I'm THIRTEEN, and i still don't have my period!! I lied to all my friends when they said they had it. Do i have to go to the doctors to make sure im okay?? And what will happen if i get my period uring school time?? i go to a catholic school where we wear skirts (and mine is a short skirt) and what if people i had my growth spurt in 5th grade (pubic hair, boobs-im 36b) all in 5th grade but its just that period that im waiting for!! help??!! whar if they see the blood and realize i lied? should i wear a pad to school even though i dont my period??