I need to get an echo scan but my mom won't take me until Friday..?

I have been getting dizzy for a couple months now but after the dizziness goes away i feel out of it, i can't focous,sometimes i get head aches, and it feels as though my hearing muffles. I had blood work done and it came back good so the next step is an echo scan. The end of the quater is this coming week and i'm a little behind in school (i missed a couple hours everyday last week for tests and stuff) I really want to do the echo scan tomorrow (monday) but my mom won't let me. I just want to see what the problem is. I hated waiting for the results for the blood work, i hate not knowing. How can i convence her to take me tomorrow?
I had actually been telling her for months i wanted to see the doctor but she never took me, she just kept saying "your fine stop whinning." when shes not a doctor. She finally took me when i got dizzy at school.
So how can i convence her? please help thanks.