If you do not get pregnant, you know that it worked. Even if you did not take it, the chances are only about 30% that you could have gotten pregnant. ECPs make an already small chance smaller. The sooner you took it, the better it will work.
Here is what you can expect:
* About 7 days after taking it you may bleed like a period (withdrawal bleeding)
* Your next real period will very likely be late or absent.
* The period after that can be delayed as well
* Your cycle dates may change
What can you do?
* stay calm and relax
* take a pregnancy test 21 days after the sex
* take another test 7 days later to confirm the results
* look for a better birth control method
Your period will very likely not start like a normal period. The hormones from the pill stopped the signals to your uterus to prepare the lining. So it will be a somewhat strange flow with a different texture, different PMS.