I was 13 when I started my period.
You need to be over 100 lbs before you start your period, you also need to have started developing your breasts. If you period is on it's way, you will have genital and armpit hair.
Some symptoms that "Aunt Flow" is on her way include increased acne
, cramping, spotting, mild to severe irratiblity, increased oil production in hair and skin, sore muscles, and tender breasts.
If you havn't gotten your period yet, don't worry! Some girls don't get thiers until they are 18 years old.
Best of Luck!