my ex has stopped paying my alimony

File a contempt action, sometimes called a Rule to Show Cause.  Unless very valid and compelling arguments are presented that the failure to pay is not intentional he will likely be held in contempt of court.  The court could reimburse you for your attorney fees, place him in jail, and require him to perform public service.  Normally, paying nothing is clear contempt.  If an individual can not pay the full amount but attempts to perform courts will be somewhat temporarily lenient if reasons are valid and not the result of the payor's poor conduct.