Plz help me to understand the child support

I'm 18. I have moved out of my moms house because she kicked me out. She was not the orginal custodial parent and owes a lot of back pay. i had been living with my grandma for roughly 16 years and while i was living with her my father (who is the custodial parent) gave her the right to get the child support so that she could pay for me. But when i moved out of both my grandma and my mother's house to live with my friend I didnt know if i was about to get any of the money to help pay for myself. i'm still in school will be graduating in may. I live in columbus, In and the laws states something about even i turn 18 she would still pay for up to 10 years because of back support can you plz tell me if this is right. if i have any right to that money so that i can actually afford to go to the doctor. please and thank you

The child support is for you but is paid to the custodial parent. Whether they share it with you or not is nothing you can do about it. If the custodial parent isn't receiving child support, then only the custodial parent can petition the court for it, not you.
If the custodial parent wants to spend the money on himself/herself, they can do that (and most of them do).
There is really nothing you can do.
And you should be able to go to a local health department for free if you can't afford a doctor.

Child support is for whomever has residential custody. It is for the child's benefit, but it is not the child's money to be given to the child.

No, you have no legal right to any child support money directly. It is used on your behalf and for your benefit in whatever way the custodial parents sees fit.

If you need to go to the doctor, there are plenty of low income and even free clinics, and I'm sure your school will examine you.