I haven't had my period in a few months and I know I'm not pregnant. What's wrong with me? – Alyssa*
It's not unusual to miss periods or to have an irregular menstrual cycle — especially in the first couple of years after you've begun having your period. Many girls also notice changes in the flow and duration of their periods from month to month.
Irregular and missed periods are common, but if you were having regular periods before or if you have not had a period in more than 3 months, talk to your doctor. Some medical problems (such as hormone imbalances) and lifestyle changes (such as stress, too much exercise, or large amounts of weight loss or gain) can cause girls to miss their periods. Your doctor will be able to look into the cause of any possible problems.