ECG, echo and troponin 0.001 all normal at 26 - your heart is genuinely fine, stop chasing that. Burning pressure in neck and jaw with upper abdominal discomfort is classic acid reflux; stomach acid irritates the oesophagus which sits right behind the windpipe, so it feels like suffocating. Your posture issue can add to the neck ache but it does not cause burning.
Next Steps
Take pantoprazole 40 mg empty stomach for 4 weeks, dinner at least 3 hours before bed, head end of bed raised, and cut tea, spice, alcohol and late-night eating. At 90 kg, losing 8-10 kg will fix the reflux better than any tablet. If it is not settling in a month, an endoscopy is the next step - you can book a Practo consult with me and we'll decide.