Even though 12-and-a-half is the average age of girls beginning to menstruate, there's a wide range of ages for girls getting their periods. Even being 16 or 17 when you first get your period is considered within the "normal" range. As for your question about weight, the opposite of what you believe usually holds true: It's girls who are underweight who sometimes don't get their periods, because a certain amount of body fat — approximately one quarter of a girl's total weight — is needed to produce hormones. Are you athletic? People who exercise heavily often get their period later than other girls. In short, it sounds like there is nothing for you to worry about, but you should ask your doctor anyway, to make sure — besides, the sooner you feel comfortable talking about your body with people you can trust, the more you'll know about it and the better you'll feel.

Regardless, feeling like a "late bloomer" is hard, especially if all of your friends have gotten their periods already and you are the only one who hasn't. But just because certain changes haven't happened to your body doesn't mean you haven't matured in areas like your personality, intellect, hobbies, and friendships. You are developing and maturing in more ways than just hormonally.

— Kate Forest, MSW