You probably can't unilaterally disavow paternity at this point, as there are prior court orders declaring you the father and you have waited a long time to raise the issue. (Also based upon what you have posted, for all you know, a DNA test would confirm paternity.)
Perhaps the mother would be interested in pursuing step-parent adoption if you indicated that you would consent.
You should talk to a family lawyer in the state at issue, so as to determine all your rights and remedies with certainty.

