I have been on bc for a month had my period sept 16-20 had unprotected sex the 22nd, took plan b the 24th had brown discharge oct 1st/2nd. am i preg?

You won't know: For sure until you have a normal period. If you had consistent use of oral contraceptives for at least a month and took Plan B within 72 hours the chance of pregnancy is extraordinarily low. Potential side effects w emergency contraception include menstrual flow changes (spotting, bleeding, early or late period). Take pregnancy test ; notify dr if your period is 7 or > days late.