By all your queries u r having oesophageal motility disorder
,it may be malignent or acqired in ur age group but contarary 2 ur history u r having it since age of 20,,,so any malignent cause is out of question, it is a neurological disease in which their is congenital or physilogical deficiancy of nerve
fibers in t lower area of oesophagus which controls t movement of lower oesophagus n which makes us 2 get senses of fullness there and it also propels t food into stomach which is just below it n empties t oesophagus,,,,BUT if their is any neurological defect food never empty t oesophagus and it overdistend t oesophagus and t sthrechng of oesophagel walls cause all your pains,it may be pain below sternum
,below throid,in t chest,in t throat or acid reflux
.......it it disturb ur life you may get a surgery done over oesophagus by gastosurgeon,it may have a synthetic new stents with spring also..