As I understand it, your ex-husband has been ordered by the Court to pay your attorney's legal fee and he has not done it. You must pay the legal fee if for whatever reason your ex-husband does not. What I would suggest is that you file a motion to enforce litigant's rights with the court so that the judge can then sanction your ex-husband for failure to obey the initial order. If your ex-husband continues to be in non-compliance with the order he will be cited for contempt of court and could be jailed if he does not pay the legal fee.
You would be far better off if your lawyer filed the motion but he or she may not want to do any further work without getting paid in advance.