Right Side Chest Pain While Running

[JJpun]

Dear Dr,
              I am a 28 year old male, classified as overweight by 20lbs, with a body fat (tape test) of 22%-24%.  My BP is high but normal 137/72, pulse 62 BPM, with serum cholesterol and blood lipids within the normal range. I have a pulmonary stenosis diagnosis that presents as a benign heart murmor.  At age 19 this was evaluated with a stress test (normal) and an echocardiogram (this provided the stenosis diagnosis).  I was given a clean bill of health and allowed to participate in strenuous cardiovascular training.  Throughout my life I have been an athlete, played football, served as a combat arms soldier on numerous military deployments, run half marathons, excelled at physical fitness tests, participated in martial arts and lifted weights.    
            I failed to run often during my last tour and gained weight (246lbs at 76", large muscular frame) I began training to increase my level of fitness.   My fitness program that consists of running, weight training and other activities.  Since then I noticed that ONLY while running I experienced a chest pain on the right side of my chest.  The pain is an dull aching pressure localized in approximately a one inch area two inches to the right of my breast bone in line with my nipple. The pain increases progressively as the run continues  between the 12th and 18th minute of the run extending into the 22nd or until the end of the run.  The pain subsides immediately if I stop and my return intermitantly if I start up again.  At times it often seems that running faster increases the pain for a short while and then the pain will subside completely.  The rhythm of the pain seems to match my breathing.The pain is a 1-3 on the pain scale and only appers in the localized area.  There are NO other symptoms (no dizziness, shortness of breath, etc) only anxiety and frusteration.
              Before this writing I had the pain reevaluated  six months ago, first with a stress test from a cardiologist (no issues suggested it may be pressure from benign pulmonary back flow no restriction) a second echocardiogram (provided the same diagnosis as the first echo) and a final evaluation with a cardiologist (suggested that it was musculoskeletal and no furthur testing required).  I have been given no further diagnosis.  The pain still persists, however it seems to lessen when my fitness level increases.  The pain does not appear for every run either, roughly 1 in 3.  Is this still a cause for concern?  What is the origin of this very frusterating problem?

Thank you for your time.

JJ