I have had that happen before as well. My doctor says that it is normal and that you shouldn't worry unless the bleeding persists for longer than normal (more than 9 days) or you are having unusual pains. The cause is as your body is flushing during your period, it sometimes is slow to pass the discharge of blood, tissue, fluid and mucus, so you get a time in between where you may spot or not have bleeding. If you go longer then 9 days, then you should see your doctor to see why you are having issues. Hope that helps.