Implantation or period

Hey ladies so I’m the birth control pill I missed up taking it one day and took a plan b because my man came in me. Later in the month I took the pill like 2/3 hours later. No yesterday I took I got my period I wiped like 3 times and got red blood in the morning, since then I’ve only have brown discharge and it’s barely getting on a pad. I have been really stressed with finals week. I took a pregnancy test about 4 days ago and I wasn’t pregnant. What do you guys think is going on?