Brief Answer:
Its unlikely to be cardiac

Detailed Answer:
Hello,
Its unlikely to be a cardiac pain and probably related to muskuloskeletal causes.
Now I guess, you don't have palpitations or tachycardia, this is just to rule out possibility of supraventricular tachycardia as cause of pain. Although, supraventricular tachycardia unlikely to cause such pain and it would also be associated with palpitations, shortness of breath or dizziness. Anyways, an ecg would reliably rule out cardiac cause. Also, anginal cardiac pain would classically occurs on exertion and relieves with rest and unlikely to persists for 5 days consecutively. Anginal pain is unlikely at this age.
Now probable cause in you is a muskuloskeletal cause, like spondylosis, costochondritis or muscular pain.
Does this pain increases or affected by neck movements or arm movements or trunk movements? If yes, then suggests the possibility of muskuloskeletal pain. Also, see for other symptoms like tingling numbness in arms, which may be associated in spondylosis.
Also see, if there any history of trauma or lifting heavy weight prior to this or if it was noticed after waking up in the morning.
I guess, you don't have any gastric symptoms or acid reflux symptoms.
So in a nutshell, you ll need examination or investigations to exactly pin point the cause out of these. You ll need
1. Ecg, as there is history of supraventricular tachycardia
2. X-ray of cervical and upper dorsal spine (AP/Lat), especially if doesn't respond to medications.
3. You may have otc like paracetamol, apply local diclofenac gel.
Hope this helps you and get back with some more information regarding symptoms.

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