You can always file for a modification but you may have to pay a lawyer to do it. The OAG looks at a formula. If you know he has other resources that can be proven you can get the child support increased. Also, the fact he does not exercise visitation can help your case. You need a lawyer -- this is not something you can do yourself.
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Yes, you can ask the court to modify your current order. Your child support order may be modified if you meet the following criteria: (1) It has been three or more years since the order was established or last modified and the monthly amount of the child support ordered differs by either 20 percent or $100 from the amount that would be awarded according to child support guidelines; or (2) A material and substantial change in circumstances has occurred since the child support order was last set.
If the attorney general's office will not assist you, contact an attorney in your area to see if they can give you a free consultation. There are also programs that assist low income families with legal issues.
The information provided is not advice but a legal perspective and you should schedule a consultation with the lawyer of your choice.