I'm having something like that myself - it started on Wednesday morning. A very sudden, very intense pain in the lower left quadrant (that's important) of my abdomen, accompanied by overwhelming sleepiness. Unlike most digestive upsets, it didn't move (that's important too). It went away, but then it happened again 48 hours later, not quite as intensely. It's been coming and going ever since, slightly less severe every time. Doctor Wikipedia says it's likely to be diverticulosis. Unfortunately, I can't call a gastroenterologist until Monday morning.
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