Contesting Paternity Help?

Im trying to contest paternity for my son. He lives in Michigan with his mother. I contacted the Prosecuters Office and they said since im in South Korea (Army) and I signed an Affidavit of Parentage which waives further DNA testing for them that they cant help me out. I can go through a private attorney which I dont have the money for. Jag can only do so much. I need help trying to figure out what to do next.