Hi . I Had My Last Period On 2/16 .

Hi . I had my last period on 2/16 . I had unprotected sexual on 3/1 . I was ovulating at this time (or so my calendar told me so) . I took plan b 3 hours later . After taking it , I had cramps for 6 days . Now my breast are swollen & my nipples are tingling . I am now receiving brown discharge & blood when I wipe for the past 2 days now. I just want to know if this is implantion bleeding or if it's plan b having my period all weird . Please help .