I understand your concern about knowing that you have a heart murmur. It is great that you have undergone further testing such as TTE and ECG and both are normal. It is not unusual that incidental heart murmurs are picked up during health screening or routine doctor's visits.
Generally, if you have been able to exercise with no significant shortness of breath, fainting during exercise or family history of sudden deaths, they are usually not of concern. However, you may want to discuss with a cardiologist if there is a need to do further testing such as exercise treadmill if you are still concerned.
