WARNING, BRAIN FOG IN PROGRESS

I will try and explain what I am trying to accomplish.

I need to be labeled disabled( boy that sounds bad), ok here it goes, I am working a very physical job, with heavy lifting, fast pace and late hours. I need to have something, that says that I am disabled, to make sure that I don't have to worry about loosing my job. Does that make sense? The company I work for, has a policy, you have to be able to fulfill all the job requirements, no exceptions, if you can't, you have to find another job. For instance, I have to fill the shelfes in a walk in freezer, it takes 3 hours, in 0 degrees( I can't do it, Lupus, RA, Fibro and asthma), my store manager only knows about the asthma and doesn't make me work in the freezer, but if upper management finds out, I will have to. Some days, like yesterday, I had to work 2:00- 10:00 PM, my huge problem is, that I am at my best energy in the morning, around 4:00 PM my energy just leaves my body ( it feels like somebody is letting the air out of a balloon), from one second to the next, I can barely move, it feeles like I am wearing a lead coat. And if I make myself work through this fatigue, the pain is excrutiating. I got home at 10:30, I walked in the door, took my Ambien and went to bed 15 minutes later.
So what I am trying to accomplish is a certain % of disability, where the company has to accomedate my needs, for instance, not having to work in the freezer or working the late shift. I am ok on the 6:00AM-2:00PM shift or the 9:00AM- 5:00PM shift. I want to work as long as I can, but the way it is right now, I can't.
So, how do I do this? Can my doc recomment the disability?
Hopefully you can make sense of my foggy mess.

Debbie