Sometimes stress, malnutrition and other things can prevent your period from coming. Doctors have a confedientiality agreement so they shouldn't be allowed to tell your father, but i'm in canada, so it might be different in the states. You can take a home preg test too if your concerned. Look into sexual health clinics in your area or youth health centres, they could help you out if you are pregnant or if you want to be tested
good luck and best wishes
jackie