The pattern you describe - burning behind the breastbone that worsens after overeating and radiates to the back, plus muscle tenderness on stretching - fits acid reflux with a musculoskeletal overlay rather than any spine disease. At 88 kg, reflux is very common and food volume is the trigger. Small frequent meals, no lying down for 2-3 hours after eating, cut late dinners, tea on empty stomach and spicy/oily food, and a short course of a PPI usually settles it. Tenderness that reproduces on pressing the muscle is not cardiac, but chest pain in a 30-year-old should be documented once with an ECG.
Next Steps
Start a PPI before breakfast for 2 weeks with diet correction, get an ECG and
LFT/lipase if pain is severe, and book a Practo consult with me if the burning persists beyond that - we may then need an endoscopy.