Hey there, I just recently turned 16 and haven't gotten my period yet. It bothers me that I don't know the reason. My mom started at 11, and my younger sister started at 12 4 years ago. I started developing (like getting hair down there) when I was 10, had a growth spurt around 11-12 (I haven't grown much since), and armpit hair (age 12 and a half). I am not involved in athletics nor am I underweight, I am 5'4" and about 130 lbs, in fact I was overweight until I was 12. And I know for sure (because I had been inspected by a doctor before) that I do not have an imperforate hymen, so that is not the case. Any ideas?