Implantation or pregs


I took a plan b November 10th. My fertile window was from 10th-16th or something like that. My ovulation day was the 13th. Last week I had bright red blood that lasted maybe for 4 days but within that time, it got brown and pink ish. Was that my period or implantion? My actual period is suppose to be this week. It’s been coming early sometimes though but then I’d bleed again my period week. Negative tests last month.