Have commission job and collect SSDI-help?

I work for Sears as a commissioned sales person. I work 15 hours per week. Under Social Security laws I can only make 1000 per month if I go one dollar over,after 9 months they will stop my Social Security.of every month I make 1001 or over.I cannot live on SSDI alone I like my job but I am getting close to the 9 months I want to stay with SEARS an I do not need to make that much. I want to continue selling. MY employer is not aware that I am Disabled. I cannot at presently work more than 15 hours per week What should I do?