What the heck is going on with me... Please - Help.

Hello everyone,

I'm a 39-year-old male, and for the last 4 years I've been having recurring episodes that no one has been able to explain. I've seen multiple specialists and had an extensive workup, but I'm still searching for answers.

What happens during an episode

The episodes can happen:

Sitting at my computer
Standing
Walking around the house
While cooking
Occasionally after eating
I've even had them after waking up

The pattern is usually:

Sudden lightheaded/faint feeling (I've never actually fainted)
Excessive belching/gas (sometimes starts before I even eat)
Upper stomach discomfort
Sometimes chest discomfort near the breastbone or under my left collarbone
Heart pounding/palpitations
Heart rate increases (often 110-140 with activity)
Feel hot or flushed
Urge to urinate or have a bowel movement
If I urinate during an episode, it's often crystal clear
Yawning
Then I feel wiped out for the rest of the day with a heavy-headed feeling

One thing I've noticed is that belching often relieves some of the discomfort, but I still feel drained afterward.

Things I've noticed
I belch even before meals and sometimes wake up belching.
Drinking can sometimes cause pressure in the middle of my chest that improves after I belch.
These episodes used to happen almost daily when they first started.
Over the last few years they've gradually become weekly, although I don't know why.
I can still walk on a treadmill for 20-30 minutes and use a Max Trainer without symptoms during exercise. The episodes are more likely afterward or while standing around.

Medical testing
Over the last four years I've had:

Coronary CT angiogram (CCTA) - Calcium score 0
Echocardiogram
Multiple ECGs
Two 7-day Holter monitors
Tilt table test
MRI brain with/without contrast
MRI cervical spine
MRI thoracic spine
CT head
CT chest
Chest X-rays
Extensive blood work including cardiac labs
FibroScan
Complete neurology evaluation (cleared)
Complete cardiology evaluation (cleared)

Currently undergoing GI evaluation:
SIBO testing
Food allergy testing
Current health
Male, 39
310 lb (working on weight loss)
Fatty liver (improving)
Vitamin D: 18.1
Magnesium: 1.8
Vitamin B12 improved from 260 to 636

Average resting HR is around 86 bpm.

Other medical issues

I also developed:
Right-sided Eustachian tube dysfunction about 7 months ago
Right-sided tinnitus
Ear fullness/pressure

I'm in vestibular physical therapy, but they don't think my balance testing explains these attacks.

My question
Has anyone experienced anything similar where:

Excessive belching or gas seems connected to episodes?
Palpitations seem to follow GI symptoms?
You feel wiped out for the rest of the day afterward?

I'm not looking for a diagnosis over the internet, just wondering if anyone has experienced something similar or has suggestions for conditions I should discuss with my GI doctor.

Thank you for reading.