Hello My Period Is Never Late, I Have A Seven

Hello my period is never late, I have a seven day cycle and my period comes on every 21 days. My period was to start yesterday on the 12 but its a no show. Last month on the 21 my period started but it lasted for 10 days come to find out I had a std that's why it was on for so long do to gonorrhea. Do you think my period is late because my last period lasted for 10 days which was abnormal