I'm a little over nine weeks post treatment myself and after having pretty decent energy levels since then, I now find myself dealing with pretty intense fatigue. The fatigue started about a week ago and at first it scared me, but then I thought I'm still in the window to still be experiencing the acute effects of the radition treatment. As I continue to research this I find hypothyroidism may be a possibility. I'll be heading back to the docs in a couple of weeks anyway, at which time I'll get this checked out. It may be worth your while to investigate this further as I understand hypothyroidism is fairly common in folks who have had radiation treatments to the neck.