Hi,
This could be due to hiatal hernia ( all the other possible problems have been ruled out).
Hiatal hernia can cause GERD.
Upper GI endoscopy, barium xray and 24 hours pH monitoring may be done for evaluation of your problem.
I have the same symptoms as you and have also had all the tests.
I have a hiatus hernia and severe reflux. It does sound like reflux, however you should go and see your doctor who should be able to give u a diagnosis and something to help ease the symptoms.
Do you experience any other symptoms? Chest pain, fast heartbeat, choking sensation??
There are lots of different sympoms of reflux which i would never have imagined until i got this awful condition.