Implantation or period bleeding?? Plan b side effect?

So i had unprotected sex 2 Thursdays ago (25th Oct) and he pulled out. I was also on the second to last day of my period. And I took the plan b pill 48 hours later. I have shorter cycles (22-24 days). I woke up this morning to light red/dark pink looking blood and have been having cramps today and yesterday that are like my usual perios cramps... is it possible it's implantation bleeding or a VERY early period due to the plan b?? According to the app my ovulation doesn't end for another 5 days and I know plan b can cause earlier periods.