Family Planning Plus

It depends on which type of birth control you started on March 13th. If you started the shot within the first five days of your period, you would have been protected on the 15th. Otherwise, birth control usually takes about a week to take effect and provide pregnancy protection. However, if you started your birth control during your period, it is unlikely that ovulation would have occurred that soon after your period. The only way to know if you are pregnant is to take a pregnancy test. If you are a week or more late for your next period, take a pregnancy test. If it is negative, repeat the test in two weeks. In the meantime, use condoms in addition to your birth control method for the first seven days of your method. Do not stop using your method unless you test positive for pregnancy.