When am I protected??

I sound a little stupid asking this, and I’m not sexually active. I am starting the pill to regulate my periods, so I really am just being nosy. But, I want to know if having sex during placebo week changes the risk of pregnancy? Like maybe it makes it higher or something? And do I have to “reset” each month, meaning when starting a new pack you have to depend on another form of birth control (like condoms) for a week? Sorry for the long post, I just didn’t think about any of this stuff when I was at the doctor’s.