aorta and mitral valves leaking

Will exercise help and how much?  I have a tread mill and can stay on it at low speed for about 15 minutes but I have great difficulty walking any distance, for example the grocery store.

[Cleveland Clinic]

There is no evidence that exercise can improve mitral or aortic regurgitation. In fact there is some evidence that isometric exercise may actually worsen aortic regurgitation, because of episodic hypertension. If the valve disorder is severe then you should seek out surgery. If not then there may be another reason why you are sol limited in your exertional ability.