Missed period super scared!!!

I had unprotected sex with my boyfriend 4 days before my expected period and he came inside (very stupid mistake from the both of us I know) but I took the plan b pill within the hour of the incident and today is now the day that I was supposed to get my period... And it hasn't come yet. I have taken the plan b pill before and I usually don't get a period until a week later, but I'm wondering if that's the reason why I'm not getting my regular period. Does anyone have any insight or can help me with any advice or reassurance??