Everyone is different, but for me, the first time I took chemo it kicked my butt, then I took the radiation. I said at that time I would take radiation 2 to 1 over chemo. It was much easier on me. I had very few side effects. I was told about all the possiblilities but I had very few. That was 24 years ago.
3.5 years ago I was diagnosed again, this time had only radiation. I was thinking no problem, I will breeze through this. In the second week I was already getting dry mouth from saliva glands going away, started getting burned around the neck, 3 weeks in, I was getting tired in the afternoon, had to take a nap around 2 or 3. Got some serious sores in my mouth and couldn't eat. And it killed my teeth. but I was getting treated in the neck and jaw area. So you will probably have a different set of side effects. But as for Sick, NO, I never felt nausea, or sickness of anykind.
all in all, compared to all the things I have had done to me, Radiation is fairly simple.
Best of luck to you, I hope it's easy for you too!