What Causes Vaginal Spotting After Stopping Junel?

I am on an oral contraceptive pill called Junel 1/20. It is a combination hormone pill. Although I do not take it at a consistent time of day I take it everyday and have not missed a pill. I have been on it for over a year now. The first day of my "off" week, I had some spotting and the spotting lasted for about 3 days and then stopped completely. Was that my "period" or should I be worried about being pregnant?