Actually, rather than getting an official Dx right now I think you should focus on finding a job more suited to you. An official Dx isn't going to help you much in the retail field.
I suggest you find a good therapist who can help you with learning how to do a good interview, maybe through some role-playing and cognitive therapy, thinking about some of the variables that may come up and preparing ahead for them.
A therapist can also help you with the physical presentation... what your body language may be conveying to the interviewer. They may also be able to help you find resources for discovering more suitable jobs.
And a good one is just a very nice support in the day to day life out there in the hurley-burley world.