Hi,
I have had a very similar problem. I have not heard of anyone else who has experienced it. Over the past 6 years I have had a lot of different digestive problems, and changing symptoms which have been variously diagnosed as gastritis, IBS and other labels. However, more recently, about 2 years ago I developed a pain similar to yours. At times it was sharp and acute in the left part of my abdomen and going around to my hip. At other times it faded into the background and was more like a gnawing dull pain. I was really concerned and have had several blood tests and an endoscopy and colonoscopy with no indications of a medical answer. During this time I have been under treatment by a nutritionalist and a Chinese herbalist/Accupuncturist. After about 12 months the pain subsided and now I am generally pain free. However it sometimes comes back in a mild way. I take this as a warning and monitor all my food and drink closely and anything that might be stressing me or creating anxiety. I haven't worked out what it is or what causes it, but I believe that eating really healthy foods, trying to relax or manage stress, no alcohol or caffeine, and moderate exercise is helping my overall condition. I also have been taking supplements for good gut flora and regular Chinese Herbal treatments. Hope this helps.