Sex before period

Hey so my boyfriend and I had sex like the day my was suppose to start (I had already started but it was mainly spotting that night but I started bleeding the next morning) I still had my regular period and bleed the same amount of days as I have always. I am on syeda birth control pill and I take it religiously every day. He pulled out and everything. But I’m just not sure how the placebo week protects you if there aren’t any hormones! I just need some peace of mind!!