If he can pay, the fact that he is in arrears is NOT a legal ground or justification to change it. Alimony can be changed if due to circumstances beyond the ex-spouse's control, he becomes unable to pay: for example, he had a high-paying job, became disabled, and lost that income and what income sources he has left or gets now are not enough to pay the alimony. But if his income is enough for the monthly payments, he has to pay and the court can force him to do so.SSDI can be garnished for alimony (SSI cannot be). You really need an attorney's help with this matter: collection on unpaid alimony arrears, garnishing SSDI, etc. can be very complex. If he only paid $1,600 over the past 5 years, he owes you another $23,400, give or take, at present, and you have $4,800 per year going forward at stake. It is well worth finding the way to retain a family law attorney.