It is not likely that mild or moderate valve disease with a normal ejection fraction could cause the severe debilitating symptoms you are feeling. A stress test is also unlikely to be positive given you age and atypical symptoms, but is reasonable given the fact that there is something deeply affecting your level of energy. If this is positive, then congenital abnormalities should be sought out first, possibly with a CT scan or an invasive angiogram. However, I think that this is also very unlikely given you severe symptoms and normal functioning heat on an echocardiogram.
Any advice would be greatly appreciated!