You are correct that forging your name on a check is fraud.  You should raise this issue with the court.  It is unlikely that you won't end up paying alimony, but it could call into question the amount of alimony your ex-wife is requesting in the pending alimony agreement.  The court might request additional documentation from your ex-wife regarding her financial status.  You may be able to argue for a reduction in the amount of alimony based on the fraud.