Plan B is very effective if taken within 72 hours of unprotected intercourse. The sooner it is used, the better the chances of preventing pregnancy. It reduces the risk of pregnancy by almost 95% when taken within the first 24 hours after unprotected intercourse and by 61% when taken between 48-72 hours. Plan B is known to cause irregular bleeding or spotting after taking it. It can either delay your periods or prepone them. While you’re waiting for your next period it is advisable to abstain from having intercourse or make sure you use a contraceptive. If your periods are delayed by two weeks or more take up pregnancy test. This is merely an advice and not a substitute for clinical examination. I sincerely hope it helps. Keep me posted.
Best luck and regards.