I Have a Question

How can I prove discrimination in the workplace? Im 4ft5 and I can almost bet thats why i cant get or keep a job. the last one I had I was handing out samples to people in the stores. I was doing great and the manager liked me, the company sent in someone to train me and she was mentioning how i would reach stuff to count on top shelves. the next thing i know im canned. but they dont mention my height, they just say there were too many people in my area, but they had told me before they didnt have any in my area, so why are they lying, anyways i can prove this? im tired of living with no income cause of people playing games, all i had to do was ask a worker there to count the stuff on the shelves, it wouldve taken less than a minute, so why the big deal? any suggestions? getting tired of all this. Im applying for ssi to see if i can get it for being a dwarf.