Have had colonoscopy/endoscopy,ct,bloodtests etc- for what reason am i getting so tired everytime after i eat? immune disease?

Depends on food: With tests ruling our the presence of malignancy or process that might produce fatigue, the answer may be in the meal content and the time of the meal. If meals are high in carbohydrates which enter the GI tract there is a need to dilute the concentrated food, Fluid leaves the blood stream and enters the GI tract causing a diminution of blood to brain resulting In drowsiness.