Exercise can even help get rid of cramps and other discomforts that you may feel during your period. Beginning with their first period, many girls expect their menstrual cycles to occur exactly on schedule. But that rarely happens. Even after they do become regular, it is not unusual for a girl to miss a period if she is sick, under a lot of stress, exercising heavily, has a poor diet, or is nervous about something. Of course, more than any other reason, pregnancy can cause a girl's period to stop.
Some girls bleed heavier than others during their periods.
But don't worry, you won't bleed too much. You have about 5 quarts of blood in your body and you only lose 1 to 3 ounces of it during your period. You may also feel some discomfort before, during, or after your period. Most of the time, cramping and other symptoms are mild and easy to control. Your pediatrician may suggest some medications or exercises to help you feel better.