Hi.
Thanks for your query.
Noted the history of ulcers when you were 18, started medicines 
Omeprazole, now 56, Doctors have just increased over, no investigations done. They said GERD 10 years ago. Have had bad burning of back throat, and increases with carbonated drinks. 
So the reasons are obvious:
You can have the following problems: 
GERD as you have already been diagnosed.
There may be associated changes in the 
esophagus like Barret's esophagus.
Hence an upper GI 
Endoscopy has to be done to confirm the diagnosis and to plan a further treatment. 
There is a big role of your psychological set up. Stress and or 
anxiety can be the major contributory factors.
Get a proper control over these by medication or by 
counselling.
Rest of the treatment as per the pathology found.