Reduced work hours?

I’m tired of my long shifts at work and I let my employer know that I was pregnant when they hired me, and that I’m more than willing to work any day they need me to.. but my back and feet are killing me! My back is so bad at the end of the night I can barely walk.

I asked her can I have my hours reduced to about 5 hours a day as many days of the week she wants to schedule me and she told me to go fetch a doctors note. Any advice? I don’t want to ask my Dr. because I don’t have a disability so I don’t want time off I just wished my employer would be understanding and try to accommodate me.