Birth Control Pills

Hey I recently started taking birth control pills to help with my mood during my period. My doctor recommended starting the pills on a Sunday so I did. I got my period on a Monday or Tuesday on the last week of the pills and it lasted three days. My question is, if that happens where my period begins and ends before a Sunday do I keep starting a new pack on a Sunday and if not should I switch to starting a new pack the day my period comes? Any help is appreciated