Question about plan b and following period?

So i had sex march 26. That was the last day of my period that started march 21. I took a plan b the same day I had sex. It's April 2 and I have my period again. Is that normal after taking Plan b? I have no qualms about it, i mean I'm super glad I'm not pregnant, but id just like to know if it was plan b that made me have my period again with only a one week break in-between.