If I had sex 3 days before my period was due and never got a period ?

If I did get pregnant within that week before my period would my period show up or would it be to late and show affects next period?

I’m currently 4 days late.

No signs of my period.

So I’ve had sex exactly a week ago.

* sex was unprotected, no plan b. Totally happy if this is possible I just thought it was barely a chance of pregnancy and I’m not sure how fast periods stop.