Please help....Spotting during Menstrual Cycle

So I've been taking birth control for a while. And this months set of pills I missed a couple. I have had protected sex recently. We always use condoms, and they have never broke, but I'm very nervous over the fact my period is 4 days late, and all I've had is a little bit of spotting. 
It started yesterday, on and off and now it's completely stopped. What does this mean? I couldn't be pregnant could I?