How can I expect my employer to accommodate my medical issue?

I recently had to go to urgent care for an issue that turned out to be obscure and I am seeking treatment from various specialists for it. In the meantime, it causes me pain to stand for extended periods of time. My doctor wrote me a note saying I need to perform seated work until the end of the month and I did submit an accommodation request through HR with the note. However, the more I think about it and look into medical accommodation online, the more worried I become. I'm a (low) manager in retail, we all know standing is part of the job. We stand, we walk around(sometimes run/jog if we have to), climb stairs. If seated work isn't possible, they can deny my request or even fire me.... I look quite young and I have high paying, difficult clients who I know would pass judgement if they saw me sitting between helping them. The only way I could "get away" with sitting would be with something like a wheelchair, but I feel like it's not right to use a wheelchair when my legs are working and plus I can't afford the cost of renting one for that long.. I tried to return to work yesterday after being gone 3 days and after 2 hours I was hunched over in pain, trying to work and ended up having my manager plead with me to go home. I can't afford to keep missing work, I already missed 3 full days last week and 1.5 shifts this week. Do I just try to work through the pain if they deny me? If they grant the accommodation, how will I be able to do this without a) irritating clients and b) not being able to constantly work (which is what I always try to do)?

Also, I don't think LOA is possible. I mean it's technically possible but I'm not sure the government would pay me short term disability because I was on short term disability for 52 weeks from sep~ 2022 to sep~ 2023 (completely unrelated issue). When I look it up it says I'm only eligible for 52 weeks of disability and I don't know if that means like, for my entire life or a set amount of time or per medical condition or what