I Need To go to the Dr but we don't have the money and my mom refuses to take me til we do, I know for A fact I need to go, how can I convince her since I'm only 15?

It depends on where and what state, county, city you are in.
There are county hospitals that are run by the county that can do what is rate your parent(s) by income.
And they use Government stats to figure out how much they are going to pay.
Some states have insurance to cover children.
Some cities have a free clinic worth looking into.