<s>[INST] i had unprotected sex on the21st  3days after my periods and had postinor2, on the24th ,,my ovulation is suppose to happen on the 26th,,,im worried that i could still be pregnant..is it possible to happen like that.if so how soon can i do a test..thank you [/INST] Hi, It is not impossible to get pregnant after taking Posit nor. The emergency contraceptive pill like Posit nor is up to 94% effective in preventing an unwanted pregnancy if it is taken within 72 hours following an unprotected sex. Its efficacy would be more if taken as early as possible following an unprotected sex. Pregnancy tests are done to tell if your urine or blood contains a hormone called human chorionic gonadotropin (Chat Doctor). This hormone is produced right after a fertilized egg attaches to the wall of a women uterus. Blood tests are more sensitive than urine tests and may detect pregnancy from about 6 to 8 days after ovulation. The home pregnancy test using an early morning urine sample can be undertaken about a week after missing a period. Hope these answer your query. Let me know if I can assist you further. Feedback is appreciated. </s>