Implantation bleeding or AF???!!

nataly

I am worried I am not trying to conceive, I had sex with my bf the 8th took a plan b right away that same day like 30 mins later probably….. I ovulated the 3 or 4…… and two days ago I started having very light brown discharge and today which is when im supposed to start I have that when I wipe and a little on my pad I thought it was my period so I put a pad on, is it implantation or my AF Is just very light