Does upper left back/shoulder pain and pain under armpit mean heart issues? Had an echocardiogram a year ago and was fine. Could it be anxiety?

Depends. Anxiety could absolutely be a cause of pain at different sites of the body. A cardiac etiology is unlikely in a person of your age. Other common causes are musculoskeletal and can be related to poor posture or old injuries.
Few things... it could be related to various issues:It could be heart disease but you are young and unless you suffer of conditions that place you at risk (diabetes, hypertension, for example) it is not highly probable esp. After abnormal test. It could also be muscular issues, and certainly could be related to anxiety. However I suggest you f/u with your dr. For further tests if needed to make diagnosis.