Pain during Nightshift. Is this normal?

I don't always work nights (I am a dayshifter, healthcare), but I am newer at my job so I am expected to cover nights on occasion. The shifts range from 8 to 12 hours long and 3 to 7 days in a row depending on the need. I have heard that sleep deprevation symptoms are different for everyone, and I think mine is intense pain. All of my muscles start aching a little over halfway through the shift and when it's time to go home it's even more painful walking out of the building and gripping my steering wheel. There have been mornings where I am sobbing in my car because of how much pain I am in. Has anyone else experienced this?