Did you have a stress test with imaging? If so these things are about 97% accurate in finding heart disease. The next test would be an angiogram which carries a very real risk of complication and I doubt anyone would do one without additional symptoms. You may be best served by getting a second opinion.
I think you need a more comprehensive panel of testing.
Have you had a vq scan?
Echo with bubble?
To start with.
Echo with bubble simply uses agitated saline and ultrasound... completely safe.
It could be as simple as gerd or hiatal hernia.
But I do think you shouldnt let it go. It's your health and you should pursue it with other clinicians if you still feel bad.
Things often get over looked!!
A vq is physiological vs anatomical.
V = ventilation
Q= perfusion= Blood/ time/ tissues ( volume)...
But it sounds almost more like gerd or a hiatal hernia may be at play here...
That would require
An endoscopy and or barium swallow, and or manometry.
Do you get heart burn?