I have been experiencing chest pain over my heart which hurts more with deep breaths/excessive talking/running & hurts on my sternum & under my breast?

Chest pain: At your age group , I doubt that your chest pain is related to your heart . I sm also worried that you are labeling your self as having Angina . Most likely your chest pain is due to muscle sourness or inflammation . This can be treated with Anti inflam drugs . Other causes of chest pain may be inflammation of the esophagus which comes from taking Asprin or Aleve (naproxen) . Get an Evaluation by your PCP .