Confused about birth control?

Denise
I need a little help please. Yesterday (9/20) I went to the doctors because I've been wanting to start birth control & this is my first time. I got the pills later the same day. The doctor told me to start taking them this upcoming sunday, but the instructions on the package said to take them the Sunday of my period. I just had my period though about two weeks ago so it would come up around sometime in the beginning of next month or whaever ,and I'm confused ? Arnt you suppose to finish the package by the time your next period comes or do I just start taking them today or do I wait till Sunday of my period or what? Sorry if I sound stupid :/ just you don't really learn this in school & I've never had a talk about this with my mom .