Hi, Thanks for posting in HCM. I have read your description and understand your concern. Plan B is an emergency contraceptive pill (morning after pill). It needs to be taken within 72 hours of having unprotected intercourse to prevent accidental or unwanted pregnancy. What you have done is proper. If you had unprotected intercourse within 24 to 48 hours from taking Plan B, you need not take it again. However, it is recommended to use protection like condoms and spermicides until the breakthrough bleeding occurs. The pill would prevent pregnancy by causing breakthrough bleeding within 3 weeks from the day of its intake. If you do not get periods by 3 weeks, you need to seek medical attention promptly, as it would require further evaluation. The failure rate by using such pills is about 5 to 10%. Hope the information provided would be helpful. All the best.