28.Norm Stress, Holter and ECHO & BP. No fam hist n non smoker. Should I get a 2nd opinion at my age? Still have chest pain and worried about heart attack

No. A second opinion will confirm what we already know. There is nothing wrong with your heart. Time to move on and look for other causes, reflux, musculoskeletal, anxiety, etc. .
Pulmonary origin. Could be chr. Pulmonary emboli or thoracic aneurysm/dissection. Start with a CT and get a chest medicine consult.