Did they not do a chest xray? Have you tried antacids with no relief? I would push the doctor for further testing to get to the bottom of things. Try to not worry about heart disease until you sort out what is going on. It could very well be stomach related. Best of luck getting to the bottom of things. Take care.
These are the symptoms of pulmonary embolism:
Fainting.
Sweating.
Coughing up blood.
Disabling chest pain with every breath. Note: The word is 'disabling.' You can't live a normal life, because you have too much pain and too little oxygen to do so.
These are very dramatic symptoms. How many of them do you have? You mention only some chest pain (which has lots of causes. If you had had the symptoms of PE, yes, the doctors would have caught it.
As to incomplete bundle branch block, it is indeed pretty common in young people. It usually does not cause any pain or any other symptoms.
So you should believe your 2 (two!) cardiologists. They really do know specialized stuff that takes years to master.
What did they suggest as a cause for your pain?