You don't mention which of the proton pumps you have taken (if any), but persistent symptoms in the presence of those drugs suggest something else is going on. The big worry would be a tumour, but you have had a recent endoscopy and that is clear. You also are helicobacter negative. There are then three other common possibilities. One is so daft you will kick yourself - you are eating food which is too hot and literally burning the stomach! The second is that you may be eating a lot of spicy highly flavoured food - common if you are eating passenger food a lot - and the third, and possibly the most relevant, is posture. You are tending to sit, and I bet slouch, at the controls for prolonged periods of time. Sit up straight, ensure your belts are not overtightened and get up to stretch a bit. With the modern ethos of locking pilots away you can't get even the little bit of exercise of wandering down an aisle and back.