Hello dear Understand your concern Plan B is 95 percent effective in preventing the pregnancy as you took with in the 24 hour after sex. It will fail in 5 percent case to prevent the pregnancy. So in 100 women only 5 women can become pregnant after taking Plan B pill. I appreciate your contraceptive practice to take paln B pill as precum or pre ejaculatory fluid contain some sperm concentration and unknowingly enter into the vagina during intercourse. Pregnancy also depend on the fertile period of the menstrual cycle. (high chance of pregnancy if you had sex in the fertile period of your cycle). Plan B pill cause hormonal imbalance due to high progesterone and that may lead to delayed in period by 7-10 days. If your period will be delayed by 12-14 days then go for pregnancy confirmation by urine pregnancy kit and or by blood HCG. If pregnancy will come positive then terminate pregnancy by the abortion pill under the guidance and supervision of gynecologist. Hope this may help you Contact HCM for further query Best regards Dr. Sagar