Thanks for posting your query. Actually these so called emergency contraceptive pills need to be ideally within 24 hrs after unprotected intercourse but not later than 72 hrs.Since you have taken it after 04 days the efficacy of it is very low. Since you have missed your periods there is a possibility of pregnancy if your cycles are regular.You may wait for a few more days and then check if you are pregnant. A transvaginal ultrasonography can pick up a pregnancy in just about 40 days!!! If the pregnancy is undesirable and it is less than 60 days you could go in for a medical termination by the use of drugs after consulting a gynecologist. The process has excellent success rate with least discomfort. You could have a heavy period and it would all be over. However it should be done under the supervision of a gynecologist to ensure complete success. A confirmation ultrasonography to ensure that products of conception have been completely expelled needs to be done. I hope I have answered your query in simple layman s language Thanks & Regards Dr M Ramesh Kamath