My mother is being dry heaving and nauseated for three months , all tests negative including egd, and other test, don't understand what is going on?

Lots of reasons...: There are many possibilities that don't necessarily involve the stomach (which is what the egd checked). Has she been tested for gallbladder and pancreatic disease, intermittent intestinal pseudo-obstruction, female problems or even pregnancy, brain and neurologic issues, is she under stress or have untreated anxiety/depression? Please address these potential problems with her doctor.