Hello doctor! my periods in july were from 24th. i had sex on 28th july and had a contraceptive pill within 72. i got my periods again today(10th aug)?

Bleeding mid-cycle: Aperiod on the 24th, and sex on the 28th, with "one bc pill within 72 hours" will not prevent pregnancy, but taking a bcp means adding estrogen to your normal cycle, and after it wears off, bleeding will occur just like it does after a normal pill cycle, when the active pills are stopped. See your provider if the bleeding persists.