I had unprotected sex around march 4 or 5th at about 11:30am. i took plan b at about 8pm. today i'm bleeding and my period isnt until another 3 weeks?

To be honest: your bleeding may be exactly what Plan B is supposed to accomplish...HOWEVER you seem a bit "vague" about the timing therefore STRONGLY advise a pregnancy test if your next expected period does not come on time! Good Luck... Hope this helps Dr Z

Plan B bleeding: Plan B alters menstrual cycles via abnormal bleeding. When 3 weeks have elapsed run a pregnancy test to be certain that you are not pregnant and use a consistent form of contraception for future sexual encounters.