Scared and needing peace of mind!

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 have been having some back pain on the lower left side for about 2 days. I start my period in about 6 days. I am just stressing out and I need reassurance. Please help me!!