Based on your history and normal ECGs, a heart attack is less likely. Your symptoms could be related to anxiety, panic episodes, or an intermittent heart rhythm problem that may not appear on a routine ECG.
Next Steps
I would recommend consulting a cardiologist for a 24–48 hour Holter monitor and an echocardiogram.
Health Tips
Also, your low hemoglobin should be evaluated, as anemia can contribute to palpitations. If you develop severe chest pain, fainting, or persistent breathlessness, seek emergency care immediately.