When my ex-wife and I divorced back in 2005 I kept the kids and opted not to have her pay child support since she wasn't making much. Now I could use the help.
I would suggest that you contact the family court in your county, and ask them for self help clinic information. They will gladly advise you of clinic hours and availability. If it exists, this will be your best free level help. They have the forms, and will help you fill them out, and get them filed.