Implantation bleeding or AF??

nataly

So I started having very light brown discharge two days ago and today which is when I’m supposed to start my period I have this, it’s not heavy to where it’s in the toilet and to where I have to change pads, I did take a plan b the 8th of this month right away when my bf came inside me and I ovulated the 3 or 4, is this implantation bleeding or just beginning of AF but it’s very light also I took a pregnancy test this morning and it was negative