I am 11 and a half and I just started my period. I do not have pubic hair or hair under my arms and my breast have not started to develop. Is this normal? I thought I would show some outward development prior to my period.
The order in which development events happen in girls can be variable. While it is not very common for the first noticeable sign of puberty to be menarche (your first period), it is not unheard of nor is it considered abnormal.
However, for safety you ought to see your doctor for a check-up. While having your blood flow first is within the range of normal development, there are some very rare diseases whose symptoms include having menarche before other signs of puberty. The vast majority of times the doctor will do a few tests, find nothing, and declare that you are one of the "rare" people whose body decided to march to a different drummer. But if the doctor happens to find one of those rare diseases; well finding things early is the best thing possible in a bad situation.