Pcp says heart ok.what causes short pain, in a small area of the left shoulder blade? i felt it while taking deep breaths and climbing stairs.

Several possibilitie: Since your pain is worse with deep breaths, it marks it as related to respiratory activity: the pleura (lung lining) or muscles and ribcage used in the work of breathing. This is not a heart symptom. Have you tried a simple remedy like ibuprofen/Advil? Chest x-ray and blood work are indicated if the pain is on-going or sooner if related to fever.