Hi Dave,It sounds TOTALLY normal. Because your outsides heal quicky, it's hard to remember the havoc that was wroght on your insides! They've been through MAJOR surgery, and there's a lot of healing to be done. On top of that, your eating is limited because of the recovery as well.
It'll get better. Baby yourself right now. Give in to the urge to nap. It'll help you heal.
Best wishes,
Denise