30 male, 6'2 89kg. For about 8 months I've been dealing with severe chest tightness and at a complete loss on what the fuck is causing it. It feels like someone is pinching my sternum and pressurising it from the inside.

I've had a stress ecg, echo, ecg, blood work and chest x ray all came back perfect. I've had an endoscopy which came back as not the cause of these symptoms but treated as non erosive reflux disease.

I literally don't know what it could be anymore, it's put me off working out as i can't get it out my head I could drop dead of a heart attack

Can anyone please point me in the right direction or give me something to try? I'm desperate now