Was it a NUCLEAR stress test and did it show proper perfusion of all areas of your heart?
Chest pain on exertion is a strong indicator of diminished blood flow to an area of your heart usually indicative of a blocked coronary artery.
I have become short of breath and have been developing chest pain with minimal activities such as showering.
This sounds suspiciously like unstable angina and a test might be to see if your chest pain responds quickly to a nitrite/nitrate.
In any case, see another cardiologist.