text: You're still young and you haven't had your period for that long.  Sometimes it takes a couple of years for your body to adjust itself.  Keep track of when you get your periods on a calendar or a pocket planner.  Mark how long you go for, then after you're done count 28 days from your last day and mark that day.  When you get close, pay attention and see how close you are to that.  Hopefully this will help guess when your next cycle will be.  And always keep some pads or tampons in your purse and backpack and locker so you have some available when you need them.  Don't worry about it too much.  Every chick goes through the same thing at some point or another.  Enjoy your womanhood! :)