Can my employer adjust my gross salary if I am an exempt (by federal definition) salary employee.

I am a salary employee who meets all exempt federal standard categories. I obtained an injury that was not per say occupational but incurred while getting into my work vehicle. My doctor had placed me unable to work for two weeks to properly care for the injury before deciding if surgery is neseccary. My salary is 2700.00 by weekly I earn holiday and sick time even though my hours aren't recorded on my pay stub, but never overtime because of my exempt status. My first paycheck while on doctor orders is not my agreed upon salary, and there's no explanation on my stub just the difference in gross salary. I was under the impression that because of my salary and exempt status regaurless of how much or little I worked im entitled to my full salary. Is my employer aloud to adjust my salary without prior consent in the state of pa.