Period or pregnancy?

I had unprotected sex on the second of November and I’m on birth control but i usually get my period the second to last day of the 3rd week right before I start the sugar pills that’s when I start bleeding and I didn’t my period. I have 3 days left of the sugar pills and I just started bleeding today but it’s light and it’s late so that’s why I’m worried? Should I be okay? Or should I test? Has this ever happened to anyone? I’ve been pregnant before so I know the symptoms all too well.