In the absence of any cardiac cause (as evidenced by a normal ECG), heaviness in chest may be due to:
1. Strained chest muscles due to overuse
2. Chest muscle injury
3. Short-term, sudden anxiety
with rapid breathing
4. Peptic ulcer
5. Pain from the digestive tract, such as esophageal reflux
Even in the causes involving the digestive tract, pain gets referred to back & shoulder due to irritation of diaphragm & phrenic nerve
So, it will be better to consult a Doctor & get a physical examination done to rule out other causes. So that proper management steps could be taken.
Wishing you a Good Health. Let me know if I need to clarify further.
Thanks & take care.