Plan b or implantation bleeding

I had unprotected sex 6 days ago and he came in me multiple times. I had just got off of my period 2 days before but when I checked my Flo app later that day it said “was a chance to get pregnant” I took a plan b that day also. it has only been 6 days and I noticed light bleeding today. Could this be a sign of implantation bleeding or the plan b?