Hi Madam.
Thanks for your query and an elucidate history.
Read and understood your problem at the age of 60 years looking like 4 months pregnant.
All the investigations you did like
colonoscopy,
Endoscopy ultrasonography, X-ray of the chest may not show everything.
Your Symptoms of pain in abdomen, bloating discomfort can be mainly die to the Anxiety and or stress, allowing you to have lots of
aerophagia meaning swallowing air, you may have dentures or the change of taste for foods and soda and colas etc.
Another reason can be you are taking foods with nuts or so , that give the similar symptoms.
I would advise you the following:
Get a course of an antibiotic and
metronidazole along with probiotics, activated
charcoal tablets and an Anxiolytic drug and see the results.
Stop all the foods and beverages which you must have noticed to cause such symptoms and I hope you will be fine.
Control of the stress and / or anxiety is the key.
If there is not much of a response, please undergo few more tests like Enteroclysis and CT scan of the abdomen.
If all the tests are normal, get an opinion of a Gastroenterologist and start getting treated for IBS, the
Irritable Bowel Syndrome.