@pza: What you're describing is unfortunately not terribly unusual. I myself found out about this connection when I experienced several GI issues over the past year. There can be several contributing factors, not the least of which is known as the "gut-brain axis". Clinically speaking, that means the communication network linking your central nervous system - essentially your brain - to your enteric nervous system - the one in your intestinal tract. When there is an interference or inflation in the latter, it disrupts the former. This can cause the exhaustion you're reporting as it interrupts neurotransmitters such as serotonin and dopamine. Fluctuation in levels of cortisol may also occur that increases pain sensitivity.

Additionally, when one experiences GI problems, there can be nutritional deficits - such as decreased iron and/or B12 - that lead to fatigue.

Try to get adequate nightly sleep by elevating the head of the bed with pillows, avoid eating for up to 3 hours before bedtime, and try to sleep on the left side to assist with the positioning for the esophagus to prevent gastric reflux. Perhaps enlist the assistatance of a dietician or nutritional counselor for the best food choices and vitamin/nutritional supplements - and always remember to discuss your ongoing symptoms with your medical practitioner to see if additional testing or a change in medication is warranted.

Please let me know if any of these suggestions help.