Whenever someone has a sensation of chest pressure, the first thing that needs to be ruled out is a heart attack or other serious heart condition. If you have sudden, new severe chest pressure or pain that does not go away, then you should always immediately go to an emergency room for evaluation.
That being said, it does sound like you've had a fairly extensive heart workup, although it is not clear from your question when exactly this was done. This workup, if recent, does make it less likely that you have a serious heart condition. However, the palpitations that you are having are still concerning, and that might require additional workup. I recommend that you discuss this with your primary care doctor
All in all, the other thing in your question that stands out is your smoking history. This is the most concerning thing, as smoking causes and exacerbates heart disease, causes palpitations, and may also cause gastric problems. So it is possible that all of your symptoms are related to this and may drastically improve if you quit smoking.
I would recommend going to see your primary care doctor as soon as possible. They will be able to help you synthesize the data from all these tests that you have had done, advise you about quitting smoking, and help you figure out if additional tests are needed.