Served With Child Support Papers

I was involved with this girl who said that she was pregnant by me. She said that she did not want to have the baby so i gave her money for an abortion. She moved out of state and i heard from her brother that she had a baby boy. I did finally contacted her and ask her if the baby was mine. She told me no and not to contact her again. so i did'nt. but relatives of hers was telling me different.

She denied me and my family of seeing the child, then had some guy call me and tell that the child was not mines it was his and to stop trying to see the child. she moves back to Iowa for a few months and then i get served with child support papers. now if I do challenge the paternity it states that if I am the father I would have to pay for the testing which i can't afford, and if I admit to being the father and just pay the support then I'll have doubt about being the father. what can I do?