Took a plan b 4 days before i was supposed to ovulate according to my period app then started bleeding a week before my period but the bleeding was very light and switched between being brown and pink and lasted 5 days is this implantation bleeding?

Can't tell yet: Plan B works most of the time, if taken soon after sex. When a woman does her home urine pregnancy test 3 weeks after using Plan B, she can tell whether her spotting was "implantation bleeding" or not. Always do a pregnancy test 3 weeks after Plan B. If the test result is negative, it was not "implantation bleeding." If the test is positive, then maybe it was "implantation bleeding."