Lynn, I was ready to celebrate when I finished rad/chemo, but ended up in isolation in the hospital with nearly zero white cells and very few red ones. I went downhill until I seriously needed help to get out of bed, and could not have walked across the room for a million dollars. This scared me more than the cancer ever did. So, have the doc check your blood levels. Being anemic can cause great weakness, and radiation can do that to you, although not usually to the extent it got me. Please note, however that I recovered and was running - not jogging - two months later. You will get your energy back!