Thank you for asking Healthcare majic. My name is Dr Ehsan Ullah & I have gone through your query. I-pill are effecetively only if taken soon after unprotected sex which is preferably within 24 hours and before 72 hours or else the pill may turn useless... Another aspect is the age of the candidate taking these pills these are not safe for the teen age group since their reproductive system is developing and they can affect the developing reproductive system since these are hormones... the recommended age group for the use of these is 25-45 years. well, in some women they can also lead to delayed menstruation which is basically one of the side effect of these drugs and it does not mean pregnancy. Emergency contraceptive pill is 95 per cent effective only if taken in time . you had sex at 4th may s morning and took these at 6th may s morning which means that you took these with 48-72 hours time... The delayed menses can be as a side effect of this pill but to make sure , you should have a urine pregnancy test precautionally and in case of pregnancy whose chances are although low, consult your physician Hope this may help you. Let me know if anything not clear. Thanks.