I was on my period and still bleeding and had unprotected sex.. i took a plan b two days after. is there any way the pill wouldnt have worked?

About Plan B...: Plan B can alter the menstrual-type bleeding for the cycle in which Plan B was taken, and sometimes the next cycle too. One should be sure to check a home pregnancy test about 3 weeks after sex, because Plan B works most of the time, but not all the time. Yes, emergency contraceptive pills work most of the time, not all of the time.