light period or implantation?

hi, so i had sex 3 weeks ago, withdrawal was used, before he finished. this was at the beginning of my cycle right after my period but days before i was ovulating. i haven’t had any of the “early” symptoms. no nausea or morning sickness or anything. i got my period on its start date which was yesterday, and had my normal PMS symptoms, but my period is really really light. it’s gotten lighter since it started yesterday. i did have a big anxiety attack and it put a lot of stress on my body and i know stress impacts your period, i just have never experienced it so i don’t know what i’m experiencing right now so someone please help.