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.
Words of wisdom by Eckhart Tolle:
"Whatever you fight, you strengthen, and what you resist, persists.”
“Worry pretends to be necessary but serves no useful purpose”
“Accept - then act. Whatever the present moment contains, accept it as if you had chosen it. Always work with it, not against it.”