Birth control question?

I'm 14, almost 15 in September if that determines anything . I'm going to be sexually active pretty soon. and for my firs time i want to be fully protective. so me and my boyfriend are going to have protected sex. Good condoms, and im definitely going to take birth control pills. I know very little about it but all the re search ive done still leaves me with a few questions. Like, i take the pill within the first five days of my period ? then once my period ends, am i still suppose to use the pill? so i keep taking the pill daily, then i have sex, and even after i keep taking the pill? so i never stop until what, 7 days after sex? or when am i suppose to stop taking the pill? im very confused so if you answer please answer in terms a young person can understand. Thank you !