Unfortunately, there's no proper civil action to bring. This is a classic example of paternity by estoppel. Even if you wanted to be declared "not the father" you could not. I don't care if you had a 1000 DNA tests to prove it.
Responses on AVVO do not create an attorney-client relationship. You shold consult with counsel for a full review of your case.
If you don't already have a lawyer, hire one to help you. The law is complex and there may be things that can be done that you didn't know about. Good luck!
If this answer was helpful to you or if it was the best answer, please click the buttons that state helpful and best answer. Please understand that all of my answers are for informational purposes only, are not legal advise, and do not create an attorney-client relationship between you and me. I am not your attorney and you are not my client unless we enter into a signed contract. My only legal advise to you is that you should immediately consult with and hire a lawyer and that you should not represent yourself. If you want to more information about personal injury, visit http://www.sainjurylawyer.com or if you want more information about criminal defense, visit http://www.giardinolawfirm.com. Good luck!
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