If your period is late you must first take a pregnancy test to confirm a possible pregnancy, or not. If the test is positive, you are pregnant and can forget the contraception and go to a gynecologist immediately. If the test is negative, you are not pregnant and you must wait until you get your period. In the meantime, you have to use a condom for preventing an unwanted pregnancy. When you start using birth control pills, you take your first pill on the first day of your period.