Work Accommodations!!!

So, long story short, I work at Ashley Furniture in Ecru, MS. I'm only 9wks and 2 days prego with twins. These babies have been putting me through it already and I'm just trying to make it to my 1yr anniversary of working at 1 steady job. So, since I have underlined health issues, carrying 2 babies puts a lot of stain on my body from legs swelling, excruciating heartburn, extreme short of breath and more. My obgyn made accommodations only for me to work 8hrs a night instead of 12 and that i may need to take more frequent breaks throughout the night. My manager said that my doctor's accommodations is a problem because if they let me work just 8 hrs somebody else will want to as well. I had to go to hire ups just to be told that no matter what my accommodations are THEY WILL ABIDE BY THEM. The night shift manager is an ssa period. But at least my lil nuggets are perfectly fine. We find out what they are March 30th.