idk what to do

I asked my dad if I can go on the pill 1 because I am sexually active but he doesn't know that 2 my periods are so heavy I have to change my tampon every 2 hours and 3 my cramps are so severe I can't even move half the time. How can I get my dad to let me go on the pill. We've talked about it a couple times and he says he'll think about it but he never brings it up again.