I took postinor four days ago during my fertile period after unprotected sex would postinor work?

It should work: Emergency contraception (EC) is used after unprotected sex, to lower the chance of pregnancy by 70%. EC is a high dose of birth control. Abnormal bleeding or spotting is a common side effect. Nausea, abdominal pain or cramping, and fatigue may occur. One should do a home urine pregnancy test 3 weeks after sex to check for pregnancy. Postinor and other EC pills work quite well, but not every time.