Iris Dear Iris, I am 13 and have been having my period regularly. The thing that bothers me is that I am still small in the chest, and don't really have much armpit hair. Thanks, Tammy Dear Tammy, Genetics play a major role in the development of your physical traits. Look around you at your older sisters, your mom, your aunts, your dad's sisters, your grandmothers. You should look something like them when you are fully developed.
Some girls continue to mature a year or two after their period starts.
If I were you, I would discuss this with my mom. She can be your own local expert on the topic.