Agree with the above; you should be checked for a pulmonary embolism. D-dimer would be a start, although further diagnostics are necessary. Be aware that doctors tend to blow off the possibility of blood clots in athletes, when in fact the risk seems to be raised. If you have any leg pain, especially calf, along with your shortness of breath, you need to really be insistent that you be checked for a DVT/PE ASAP. Unrelated to a potential clot (I think), did your blood work include sodium, potassium, and magnesium levels?

If you're looking for a cardiologist, David Cannom in Los Angeles is really good and is known for his work with athletes. He's been around a long time and really knows his stuff, and is on top of latest research and innovations. He would definitely know what to look for heart-wise; I suspect that he would also recognize the possibility of a PE, even though that's not his specialty area.