I took postinor after sex. my period has been delayed by 1 week now. i have been having nausea, headache, dizziness and so on. could she be pregnant?

Small chance: Plan B, Postinor 2, and other brands of emergency contraceptive pills can alter the menstrual cycle for the cycle in which Plan B or Postinor 2 was taken, and sometimes the next month's cycle too. One should be sure to check a home pregnancy test about 3 weeks after sex, because emergency contraceptive pills work most of the time, but not all the time.