What does it mean when i already had my period but had sex, took a plan b pill and a few days later had wet red-brown discharge or bleeding?

No problems here.: Minor bleeding after Plan B is a side effect of the hormones in the medicine. As long as the bleeding is not severe and your normal period returns the following month you should be okay.

Plan B can cause: bleeding. Red-brown discharge is most likely blood being cleaned from uterus. Potential side effects w emergency contraception includes menstrual flow changes (spotting, bleeding, early or late period).