Shoulder pain, chest heaviness when breathing deeply. Normal ECG

I m a 17 year year old male, last night while on the computer I got a pain in my left shoulder , over the next 5 minutes it got worse, i tried to wait it out but the pain wasn t going. I then noticed i felt a heaviness in my chest when i breathed in deeply, i decided to lie down and I was alarmed to find that I could hear my heart beating loudly, my mum could also hear it so she decided to call the ambulance. They arrived and I had an ECG , all the tests came back normal and the pain began to go away so I didn t go to hospital. However its been 24 hours and my chest still feels heavy when I breath in deeply and my chest would hurt if I was to jump or run on the spot for example, also my heartbeat can still be heard loudly when i m lying in a certain position.