Pain between chest & stomach always diarrhea. when i drink fiber drink pain subside. been like this for more than a year or so. not like regular pain?

Gnawing?: Chronic diarrhea suggests irritable bowel syndrome; I presume you have had other causes like infection, inflammatory bowel disease, etc. excluded by tests. Pain, "not like regular pain", in the upper abdomen may be due to diabetic gastroparesis. Emptying of food from the stomach is delayed leading to retention of stomach contents. Frequent small meals & avoidance of high fat & fiber foods may help