Generally The Emergency Contraceptive pill is taken after a unexpected act of sex to prevent pregnancy. It acts within few hours of intake and makes the environment unfavourable for the pregnancy to occur. BUT It doesnt kill the sperm or the ovum. Hence even if taken it has chances of failure too. While you were correct in taking the pill after the first sexual intercourse. The second and third acts were "acts of pure misadventure" Now nothing can be done to avoid pregnancy. Every act of sex may NOT cause pregnancy as though the sperms are deposited in the vagina at each sex act, the pregnancy can happen ONLY if these sperms meet a ovum. The Ovulation happens roughly around the 14th day ( in a lady with 28 day cycle ) BUT it is not a regular happening. So If your intercourse have happened around mid cycle, go for Gynec counseling. Taking another ECPill is going to load your body with lots of hormones and it will make your menstrual cycle very irregular for the next 6 months......so never even think about it Just wait for the next menses. If the date is missed you can do a urine pregnancy test on an early morning sample of urine and see. if it is negative, you have avoided pregnancy. But if it is positive, it would mean pregnancy has happened and then you may have to seek help from Gynecologist. Just like Emergency Contraceptive pills, some times insertion of a copper T can also prevent pregnancy. So seek a Gynec consultation.