While it is normal to have irregular bleeding when you begin to menstruate (have periods for the first time), you should not have to change your pad every hour. This is too much bleeding. Call your health care provider and let them know that you started your period and how many times you needed to change your pad and if the pads were lightly covered with blood or if they were soaked. Your periods may be different for the first couple of years and you may find that your next period is a lot lighter.
Read more about menstrual periods.