"Feeling dictated to about my walking"

I attend the renal unit at the VOL hospital but at each session, especially today, I feel dictated to about my walking. On the days I come in my mobility is poor and two nurses kept saying it was caused by my high potassium but I been told by my GP and physio that it's caused by stress as I am always fine before I come in to the unit. I really am fed up as I feel like I am being spoken to like a child  - I am in my forties and not a 3 years old. 

I also want to query why I have extra time on my session when I don't want to. I am now getting to the stage that I don't want to attend for treatment at the unit on the days of treatment.