I don’t know if this will be helpful or not. Shortly after RAI, I began experiencing the symptoms you are describing. It was awful. My doctor ran every test imaginable (really yucky ones) and my gastro system checked out normal. Finally, he suggested I try antidepressants. I insisted I was not depressed and that was NOT the problem, but he requested that I humor him and just try them. To my surprise they worked. For some reason my depression manifested itself in this manner, rather than the “blues”.