I am 25 and have been on Yaz birth control since december. My menstrual cycle has always been on schedule until this month. I should have had my normal cycle starting this past saturday but instead I started, very lightly, spotting dark yesterday. I went ahead and took a pregnancy test yesterday just to be on the safe side and it came back negative. I also read that spotting could happen at the beginning of pregnancy, but I haven't missed any pills. I also read some bulletins posted by other people who take Yaz and they say that extremely light periods are normal. Is this something I should be concerned about?