It’s normal for adult women to have a menstrual cycle that ranges from 24 to 38 days, and for teenage girls to have a cycle that lasts 38 days or longer. But every woman is different, and each person’s cycle can vary from month to month. During some months, your cycle may last for more or fewer days than the previous month, or it may start earlier or later than it has before. Sometimes, you may even have two periods in a single month. If your cycles are on the shorter end of the spectrum, you could have your period at the beginning and end of the month with no reason for concern. But if you experience bleeding outside of your normal menstrual cycle and suspect you’re having a second period, the first thing you should do is figure out if it’s spotting or menstrual bleeding.