My ex has never paid child support.. our son is 13 and the ONLY time I have ever received money is when he was arrested and his family paid for him to get released the money was put towards his child support. Probably about $800 over my sons 13 years. He was recently approved for SSI disability. Will I receive a lump sum for behind support?

No, the child can apply for benefits that will start when fathers were approved.

This does not pay the child support, merely government funds dependent children get. Has nothing to do with support