Pain in the chest, shoulders, and arms is often tied to excessive or strenuous use of the arms. This seemed to be accentuated when you tried to mow the grass. Even though it acted up during your meal, it does not sound like reflux. First try regular anti inflammatory medications (ibuprofen/naproxen), as well as a topical anti inflammatory like Aspercreme. Topical ice would help also. If these measures don't work, seek out a chest x-ray from your doctor, who would also check for cardiac causes.