Chest Tightness and Sharp Pains

Hi.  I am a 36 year old in good physical condition with no history of chest pain until two months ago.  In fact I have been doing sprint triathlons for 2 years and was ready to do another one when I experinced chest pain after a 5K run.  I had a cold that week and thought I had just pushed it.  My doctor said I had pneumonia and put me on two courses of antibotics.  It did seem to get better for a couple weeks but even though my chest ex-ray is perfectly clear, I am still not able to exercise without shortness of breath and I often have tightness in my chest.  I also have short sharp pains in my chest and underarms.

They are testing me for asthma but I don't ever have a cough associated with teh chest pain.  The only other thing I can think of is that I do have acid reflux but I take medication every day and have for 8 years so I don't know why I would get chest pain/tightness now.