10 days dpo brown and red spotting

my period is due between tomorrow and the 18th (according to my trackers). I took plan b at the beginning of the month right after unprotected sex. He didnt cum in me, he withdrew. I thought I started my period yesterday because i spotted semi-dark brown and some red blood. No pink. Today theres nothing much. veryyyy dry brown cm and a little fresh red blood. im getting more cramps today too. i know i have to wait to test but im kinda freaking out once i read about implantation bleeding....does this sound normal?