Based on your description,I presume that all necessary tests have been done. I presume that stool for giardia is negative. I also presume that H.pylori stool test or Urea breath test is also negative . And as you have mentioned blood tests,I also presume that tests for coeliac disease are negative as well. Do you have any other symptoms such as constipation/diarrhea/weight loss/nausea/vomiting etc. Assuming that all investigations are negative, one of the possibilities is Irritable bowel syndrome. Another possibility is that of certain food allergies . Do you feel discomfort after consuming certain types of food? You may maintain a food diary and record the food types that you consume and note down your episodes of pain. How about your general health? How is your weight and general fitness ? I presume that Complete blood count, Liver function tests etc are also ok as you have said. In a nutshell,my advice would be to maintain a food diary and note down the episodes of pain to find out any specific food intolerance or allergies say for example to milk/soy/eggs etc. I would require some more information from your side to suggest further advice.. Should you require further assistance, please feel free to post more information here. Best regards