As you probably know, it takes time even for a veteran. The chemo and radiation wears you down physically, including your immune system, which is probably why you keep getting thrush, a fungal infection. The Oxy pain meds can also make you tired, and has side effects of its own. I assume you are doing the salt water, baking soda, and other oral rinses? Diflucan, flocomizole, is often prescribed for effective treatment of Thrush, and I often say to change your toothbrush to keep from reinfecting yourself. Thrush, basucally a yeast infection, feeds on sugar, alcohol, yeast and processed foods, so you may want to look into that too. Good luck with your PET. Mine is 2/19.

You might want to ask the doctor for a full blood work up besides the usual CBC to include a the TSH, Vit D, testosterone, and A1c to see if there are any deficiencies.