How do I get the county to up child support?

My son is now 7 yrs old and most of his life I have had to work two jobs just to make it. I am now unemployed and trying to make it on 119.80 a month that is what is court ordered child support. When we went to court when my son was about 18 months old they court ordered 100.00 a month. Its now been over five year and they have yet to change it. The extra 19.80 is to pay the back child support of 5000.00 because he didn't pay anything for about 5 years. I know my sons father makes over $11.00 an hour diving trucks. Over the last 7 years I have paid all expenses like child care, medical and dental insurances, medical and dental bills, clothing, even the medical bill when his dog attack my child. what can I do? The county just keeps telling me that it will be like 6 months to a year before they will even look into it.
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You can file an appeal with the courts for them to look over his income. They had to do that with me. Cause I owe 1500 right now and they are threatening to take my license away so I had to file an appeal so they wouldn't take my ability to drive away. But I know they can review his income at any time if you request it cause my ex did that to me.
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