There is way too much of the story missing to conclude there was any conflict of interest at all, and obviously nothing to indicate fraud. In addition, you knew this during your "last divorce," whenever that was, so it is curious that it is coming up now, apparently after the fact. Why did you not discuss this with your lawyer when you realized who your ex's lawyer was? Was the issue raised with anyone? There no way to conclude you have a valid complaint, but even if you did, the decision-maker will ask those same questions and perhaps wonder if you want a "do over" in the case. See a lawyer to review all the facts.
I agree with Mr. Riddle, far too few facts to make an accurate determination as to a conflict of interest. First and foremost, when you say "my lawyer" that implies you had retained him either for the divorce or for a prior engagement. I find it highly unlikely you had retained him for this divorce only to have him accept payment from your wife for the exact same case. If you only sought his counsel and did not retain him he was not your attorney. If you previously retained him for another issue it is likely, depending on the nature of the previous case, that there was no conflict to begin with. Finally, a common misconception is once my lawyer always my lawyer, this is not the case, as stated above, retaining a lawyer for a single action does not make him/her your lawyer forever.