Birth control help


So I go to my doctor and tell her that I need birth control for my period. She says she’ll give me the lowest dose and that “because I’m not taking it for birth control it won’t matter if I take it at the same time ever day” my dad then turns around and says “the lowest dose won’t help prevent anything during sex, so this isn’t actually birth control” I’m obviously not gonna tell my parents that I’ve had sex before but is that true? The lowest dose doesn’t work? I thought it all worked?

UPDATE: can I just say how much I love women and this app 😂