You should talk to your mum about this - she had been through it, she is a girl after all. At least see your doctor, changing your pad every hour at age 13 seems unusual.
dont sweat it, mine did the same thing.
did you recently start having periods?
because almost everybody is irregular when you first start.
its normal. if you notice that after a while its still not right
then you should seek a doctors advice.
the heaviness of a period changes usually in the course of a periods lenght.
heavy to light
light to heavy
heavy light heavy
light heavy light