Menstrual cycles are extremely variable between individual women. Therefore, you should not compare the length and heaviness of your own period to those of friends, as it is likely that your short three day periods are simply your normal healthy variant. It is quite common for teenage women to have heavy, irregular, or long periods. Therefore many women say that there periods are 'shorter' or more normal now then when they were much younger. This is a very normal phenomenon. You should not worry
about the length of your periods per se. However, if you start to miss periods, or if they become very irregular, or if there is heavy bleeding, these might be symptoms that should be evaluated by your doctor
. As always the diagnosis and the management of your particular condition will require a physical examination by your personal physician. Setting up an office visit with your primary care doctor
or your OB / GYN doctor might be advised.