Birth control.

Ariana🍒 • lost in the sauce ~
So, i'm starting birth control this month due to my periods being super irregular, i'm trying to reulate them. my doctor prescribed me Sprintec. i know to take it on the sunday of my period. my question is i'm going to be sexually active sometime in february so will it be working then ? and do i take it everyday after that sunday ? also will my period be regulated so that in february i'll know exactly when i get my period so i can be sexually active not around my period ? i'm just so confused. please help. my doctors office is closed so this is my second option 😂