Dear friend, welcome and thanks for entrusting your query here at HCM!
I am Dr. Prasad Akole (Critical Care Expert- http://bit.ly/Dr-Prasad-Akole) and am glad to address to your query here.
As your necessary tests are negative, the cause of pain is unlikely cardiac.
is an invasive test requiring heart catheterization and is not free from complications. I would not advise it at this stage.
Has an Xray chest been done?
Do you also get nausea
in the arm? Do you get breathless on exertion?
Are you anaemic? Are blood tests done?
Please seek a second opinion
of a good cardiologist to know if he too feels it likely cardiac. All depends on the physical examination and ECG/ echo interpretation.
Please consider musculo-skeletal and other causes which cause such symptoms.
I hope you are fully satisfied with the guidance I gave.
Hope I have answered all your questions. I would be glad to answer any further queries. Please ask for any clarifications before closing and rating this answer.
Thank you and Good luck!