Kayl,
This is a difficult question to answer. Which valve may or may not be causing your symptoms is difficult to determine without seeing you. I would actually argue against the mitral valve as the dimensions and regurgitation that you describe are not wholly unexpected with a prosthesis. I am more concerned about the aortic valve, assuming that it is not a prosthesis?
I would recommend that you consider 3 things:
(1) Is it known that you do not have coronary disease? If not then check that out first.
(2) Consider an expert opinion at a major center.
(3) Consider an exercise echo to see if one of the valves worsens with exercise.
Hope that helps.