Just need reassurance

Julia
I started birth control 12 days ago, and on the 10th day I took my pill an hour later than I usually do. That night he came inside me. But for the past two days I went back to normal time again. I understand that my chances of pregnancy are slim but for some reason I feel very nervous. How can such a tiny pill prevent me from getting pregnant?! Also, what is considered the appropriate time frame to take your pill in before it's considered a missed pill? 1 or 2 hours? More? This is my first relationship and first time using the pill so I would just like reassurance I guess from those of you with experience. Thank you. ❤️