Hi... If the doctors (physician/cardiologist) have concluded that everything is fine with you physiologically, we can attribute this pain to psychological factors.
Are you in a profession (military) that requires beyond average physical/mental stress?
If yes, it is possible that this is conversion, i.e., your mind is creating this physical pain to diverge your attention and create a guilt free reason for your inability to perform a task.
There might be other psychosocial factors as well.
Next Steps
Consult a Psychologist.
CBT along with Motivational Counselling and Lifestyle Guidance is required.
Health Tips
Mr. Gunjan Maithil
Senior Psychologist
Cell: Nine Six Seven One Three Zero Three One Three Four (whatsapp)
Website:https://gunjanmaithil.wixsite.com/therapy
App: http://wix.to/fECHB08?ref=cl