Severely bloated abdomen

I am a 56yr old woman, usually fit and healthy, very active outdoors, healthy diet, 169cm and very slim.

For almost 7 years I have experienced:-

Slightly bloated abdomen, especially noticeable towards late afternoon

Very tired/exhausted immediately after eating. (what I ate made no difference)

Occasional indigestion, and gnawing feeling under ribs. (endoscopy showed “mild stomach inflammation”)

Bowels normal

3 years ago above symptoms more noticeable and intrusive.

Abdomen swollen earlier in the day now and increasingly noticeable.

Felt hot and flushed around late afternoon when stomach more swollen.

No indigestion, heartburn etc now.

Breathlessness (increasing) when abdomen swollen.

Mild headaches

Becoming increasingly tired/exhausted.

Past 12 months – above symptoms have become very uncomfortable and impacted severely on my quality of life.

Abdomen bloating so uncomfortable – feels so heavy, and as though it will burst at times!

Clothes I wore 12 months ago no longer fit, and yet I have lost weight.

Burp often (but little wind)

Tired/exhausted, burnt-out feeling constant now.

What I eat doesn’t make any difference: Low fibre, low irritant diet and gluten free diet made no difference.

Stomach/Abdomen can swell up in a few seconds! Stomach feels “full” all the time. It swells also as I eat/drink.

[At times it feels as though I’m being strangled at the waist, and kicked in the stomach at the same time.]

Extremely tired after eating and more breathless now – stomach/abdomen now takes up ‘all the room’, puts pressure on other organs, and feels so heavy.

But, the bloating is not constant and still (usually) wake up with only a slightly bloated abdomen - after a glass of water/cup of tea it expands! And when I walk with just this fluid you can hear it (like a hot water bottle).
Nothing gives relief.
I have seen several GP’s, and 3 gastroenterologists.
It’s not cancer.
No ulcer.
No helicobactor pylar
Not coeliacs disease.
Not fructose intolerance
Not lactose intolerance

I have had:-

Endoscopy (2)(showed mild gastritis, stomach inflammation)
CT Scan of Abdomen – Normal though liver slightly enlarged)
Ultrasound
Barium Meal (small bowel studies)
Gastrogaften
Bloodtests

Pescribed: Gaviscon, Mintec, Nexim, Np7, Simethicone, Carafate, Zantac, Pariet, Flagyl, Motillium
none of these gave any relief – they were either useless or aggravated the condition/symptoms.

GP’s and specialists just “don’t know” and apply the term IBS to cover such conditions, and have no (other) treatment/advice to offer!
Meanwhile the extreme discomfort continues and is becoming increasingly worse as time goes by.
If anyone else has this condition or has any advice, or answers in regard to ‘dealing’ with this condition it would be greatly appreciated!