Looking for advice

I'm a heavy bleeder

(Crime Scene) and I started my period yesterday. I have to go to high school in the morning and I'm freaking out because I have to change my pad every 10-15 mins, I'm messing up my clothes, extreme cramps and upset stomach. I've already missed a lot of school because of other health issues. And yes talked to my lady doctor about a week ago and this coming up week I'm getting the birth control that they put in your arm but until then I don't know what to do. Please help