Sherry, please bear in mind that we're all different and that you'll get lots of... interesting... responses. For me it was mouth sores that, within a couple of weeks, reduced me to a liquid diet. As the sores expanded even that was tested. Burns to the neck followed within a week or so, along with fatigue.
RT is a very tough road. Please be sure you ask your docs for everything you need to ameliorate the side effects - pain medication, mouth numbing agents, burn creams, saliva replacement fluids and any other meds to deal with the more subjective EFX like depression, anxiety, sleeplessness, etc.
Those of us who've been through the mill on this have all come out the other side, and you will too!