"i had unprotected sex two days after my period ended. i took the plan b within 12 hours. two days later i started bleeding lightly and it lasted 3-4 days. i didn&#039;t think this was a normal period so i still expected to get mine at the normal time. i didn&#039;t come. i freaked out. i was one week late and decided to take a pregnancy test. negative! that same night i started my period. maybe the light bleeding was the plan b working and it reset my cycle because 28 days after that i got my period. i&#039;m now on birth control. no kiddos for me thank you very much. thanks plan b!!"