sex on birth control

hey, i'm new to birth control so yeah, i started my period on thursday and so my doctor told me to that it that sunday, so i did. i've taken it every day, same time. everything. she told me after seven days i'd be protected. so last night my boyfriend and i had sex and he, you know, inside me. i was just curious because yesterday, sunday, i took my pill. and i counted that that birth control yesterday was my 8th pill. i've heard others say if you've taken 7 you're fine.