Is it normal (by able bodied people standards) to experience excruciating pain when they first start jobs?

Okay, I’ll start off with the fact that I am disabled. I can list some of the relevant stuff but I am. But I am being told by the woman who birthed me that me being in excruciating pain is normal. She literally laughed at me.

I was at work for around 6 hours. On my feet for around 5 1/2. I was checking dates for experations and neatening shelves. I genuinely found it FUN! But by 30 minutes I started getting pain and by 3 hours in I started feeling like I was going to cry and getting dizzy. By 4 1/2 hours (after a 30 minute break) I started wanting to scream, getting random intense dizzy spells that caused me to not be able to properly control my movements, and feeling like I was going to collapse due to the pain in my spine.

I work out 3 times a week. I walk around the house veery single day. I go out every weekend on Saturdays, for hours. I don’t walk and stand too much but it’s because every time I try it causes horrible pain. This is my first job ever because I had to get help from a government program that helps people with disabilities get jobs. I’m seriously questioning calling my case worker tomorrow and see if I should get something different. But it’s only the first day and I’m worried my parents are right and I am overreacting. But they also have a habit of never believing me about my disabilities and have flat out told me that I’m faking how bad it is.