I Took Plan B Pill On 9/8 And Got My

I took plan b pill on 9/8 and got my period on 9/21 lasting about 5-7 days. It was a little heavier than usual. Around 10/1 I began to have little brown discharge (normal as I get it every month) but on 10/5 I began to bleed as if I were starting my period again with brown discharge. It's now 10/8 and still having brown discharge and have been wearing light tampons. I have not been sexually active since 9/5. Is this irregularity due to the plan b?