SRT side effects

I am undergoing 21 SRT treatments for skin cancer to the top of my skull. My current age is 77 and I’ve always been very active, wife and I even ride e-trikes although balance has never been a issue for me. I’m currently just finishing treatment 10 and at about 5 I noticed fatigue that I reported and it was quickly attributed to stree so I let it go. This past Monday my treatment was at 9AM and throughout the day I was fine working in my pole barn. I came in the house at about 2PM had a light lunch and waited for my wife to come home which is normally around 7PM. At or about 6PM it suddenly felt as though I had quickly spun around about 30 times. I couldn’t walk and was extremely nauseous. It continued until I went to bed. The next morning when I got up I was no better and my wife immediately took me to our doctors office. It took a wheelchair to get me from the car inside. When the doctor saw me and I told her what I was experiencing she said that she wanted to get the nausea under control first and gave me a very small pill that dissolved under my tongue. Within minutes the nausea ceased, and the doctor checked my ears to be sure that I had no ear infection which I did not. The doctor hinted that this was caused by a accumulation of several factors the SRT, nasal drainage, and weather changes. No one seems to associate the actual cause being SRT and at this point in time having 11 more treatments I’m very concerned what might happen next.