I applied for SSI only. Got it. Had it for 4 years and worked parttime and had enough credits finally for SSDI in Oct. 2011. However, for some reason they denied me the SSDI while still giving me the SSI. I appealed and won at judge level. Will I get SSDI back pay from Oct. 2011 to date or did SSI take it all? (I received my SSI back pay long ago.)