Hi, thanks for asking in Healthcare Magic. Abstinence or withdrawal pull out is associated with a highest failure rate. Although unwanted 72 contains Levonorgestrel, a progesterone which prevents conception and can cause withdrawal bleeding, it will not protect you from the subsequent exposure you had. Since the second exposure was too close to your periods date, and happened after you took the pill, unwanted 72 may not have been effective. The withdrawal bleeding should have come within 5 to 7 days. Since the pill contains high level of hormone it may have disrupted the menstrual cycle and may have caused the delay. But still in your case, the chances of pill failure is more and so you have to rule out pregnancy through urine and blood tests. If your pregnancy tests are negative, then visit your treating Dr and follow a regular method of contraception suggested by your Dr and avoid using ECP frequently as it may completely disrupt your menstrual cycle. I hope this is helpful to you.