Period, breakthrough or implantation bleeding?

You need to take the pill for a whole cycle, everyday, before it is effective as a birth control method. I'd say that since you never took it every day or for a whole cycle, you're just as likely to fall pregnant as anyone else who is trying to concieve. But as to whether you are late or not... that's really confusing, with all stop-starting of taking the pill I'd say you've stuffed this cycle right up and don't have any chance of predicting when you are due... and therefore if and when you are late. So it could be an implantation bleed, sounds light enough, or else its a period just not quite sure whether to come or whether to go. The only way to know is to take a test.