Suggest Treatment For Pain And Knot Like Feeling In Abdomen

My mother, 84 Hispanic, has complained of a knot in her stomach (and minor pain in that particular area), she feels weakness in her stomach (I’ve never understood what that means), suffers from constipation, often feels bloated (gases)… I could go on forever. These complaints have been off and on for more than five years. An extensive array of tests has been completed i.e.: X-rays, stool samples, testing of the colon and esophagus, a swallow test etc. I believe doctors have done their best in an attempt to find the problem; all tests negative. Yet still, her problems (complains) continue. As of about a year ago I stopped listening to her complaints and have come to believe that it is now a mental problem or a search for attention. There is no stress in her life and she lives in our home. Could I be wrong, and is there anything else that can be done?