My period was 3 days of spotting 2 which seemed like a period is this my period or implantation bleeding ??? i'm really confused i had sex 3 weeks ago

Who knows?: Implantation bleeding is actually pretty unusual. That would be pretty late for implantation bleeding which should happen about 10 days after impregnation. If you were pregnant you should probably have a positive pregnancy test by now. Use a home pregnancy test, if it is negative, check again in a week. If it is still negative you have your answer.