Sorry to hear that @cactusk .... just pace yourself - if you are weary, have a rest - hold off on the walks for the time being.
Get someone else to do 'stuff' for you! .... it could also just be an accumulation of 'everything' hitting you now that your diagnosis, surgery is over & you can relax a bit. I was lucky & didn't feel fatigue at all & only had a little bit of skin breakdown at the end of the 4 weeks .... keep your fluids up too.
take care xx. Let your Rads Nurses know how it is affecting you too - so they note it down xx