Does Postinor-2 Taken 10 Days Before Intercourse Prevent Pregnancy?

i took postinor-2 10days before after having un-protected sex! now i am feling abdominal cramps, my nipples hurt sometimes and tender also, and i also eat more i.e sometimes i crave for food. is there any sign of pregancy?? although i took a pregnancy test yesterday and the result was negative. Also i missed ma period date..!