Help?? Spotting//period//pregnancy???!

I’m on the last day of my ovulation and I’m supposed to start my period on May 2. I took a plan b about a week ago (2 days before eve said i was supposed to ovulate) i went to wipe (April 17) and the toilet paper was stained a very faint pinkish color, now it’s april 18 and it’s still like this. Is this a light period? implantation spotting? or because of the plan B?? Also i took a pregnancy test today and it said negative.. like solid negative no faint positive or anything. Solid negative... is this accurate??