Hi, I have gone through the query and understood your concern. Emergency contraceptive pill, when taken prior to ovulation, inhibits ovulation. Thus, pregnancy cannot occur. The discomfort could be due to the increased pelvic congestion as a result of the high hormone content in the pill. Sometimes, cyst formations are observed in the ovary. Your next natural period also may get delayed by a week or two. If the pain is persistent and annoying, if you become overdue by ten days, please see a specialist for further support and management. A sonogram of the pelvis, preferably in the trans-vaginal route, is most helpful. Hope your query has been clarified. Take care.