I am not licensed in SC, so my advice should be considered in that light.
Typically, if you have a court order for child support, and the person ordered to pay it is not doing so, then you would have to go back to court for the non-paying ex-spouse to show cause why the payments are not being made in compliance with the court's order (it's an Order to Show Cause) -- See http://en.wikipedia.org/wiki/Order_to_show_cause.
You can go the lawyer that handled your divorce, if he or she is available, or you can look for a new local lawyer. You can try the South Carolina Bar Association for either a referral or for a free or low cost legal clinic -- http://scbar.org/PublicServices.aspx
You may also want to consider calling the Horry County Family Court for suggestions (they will not give you legal advice, but may guide you in the filing of paperwork or provide other useful information).
This answer or response should not be considered legal advice, and does not create an attorney-client relationship. If you have further questions, I would be glad to discuss your situation further. I can be reached at US - (801) 746-6300, or online at -- http://www.lewishansen.com/attorneys/robinson.html