Even though 12 is the average age for your periods to start, the normal range is between 11 and 16 years old. The age you start depends a lot on your genetics and also your body mass index. Ask you mum when she started her periods. Are you quite slim or do you play a lot of sport? In any case, you shouldn’t worry until you are at least 16. In fact, enjoy your period free time! If you are very worried, it certainly wouldn’t hurt to see your family doctor just for a general check up and to ask any more questions you might have. As hard as it is to not compare yourself to other girls your age, remember that every girl develops in her own time.