Should I be worried?

My boyfriend came inside me one day into my sugar pill time. I have been consistent for the rest of my pill pack, but there was one day that I’m suspicious about. I remember taking the pill out of the packet and that day’s dosage is not there, but I don’t actually remember taking it. But surely I wouldn’t have just left the pill somewhere? I’m assuming I did take it and am just forgetting now. This was about 12 days ago. Should I be worried? Is there a big chance of me falling pregnant?