Congratulations! That SSI can be hard to come by sometimes. And I know this is a huge burden off your shoulders.
If you haven't gotten your first check yet and need money, contact your local SS office. Take in your letter of approval and they can cut you a check for up to but not including $1000. So basically you can get $999.00. It will come out of your back pay but at least it will be some money until your checks start coming.
My DH is on it but he was approved immediately. Minus one leg, six discs, has cadaver bone fused to 7 vertebre, a metal rod in one thigh bone and a large metal "ladder" holding his spine together. Not much of a way they could have denied him.