Wave of nausea/fatigue after eating

Adominal pain and discomfort.  Normal endoscopy, normal hida scan, normal labs...Tried PPI with no relief. Eventually had gall bladder removed. Discomfort then morphed to "nausea." Being treated now for anxiety as  no one can figure out why I have continued nausea. I still wonder if there is a GI component because...
I get a severe WAVE nausea, tingling, and pronounced fatigue (have to lie down) exactly 40-45 minutes after eatng breakfast--.-- every day! (most of the rest of the day there is just mild discomfort and generalized fatigue-- whcih the anxiety meds do seem to help).
Why?