Burning in chest. Underlying decease!

I am a covid survivor, my rt pcr came negative 9 days ago it was a mild case, my hrct score was zero my d dimer few days back was .35 and crp was 2.3. But few days back I felt burning sensation in my chest followed by niddle like pain I consulted to a physician and then a cardiologist both suggested acid reflux and asked me to some daily life changes which I did,but since yesterday day I am feeling burning sensation in the middle of my chest where ribs meet,sometimes with moderate and sometimes with mild intensity,today I checked my stool it's one side was dark green and other was faded yellow,but consistency was normal,i dont feel vomit or pain in my stomach am taking antacids (superia dsr and mucain gel) in morning which doesn't make any improvement. I dont smoke or drink ,I am eating only home cooked food without oil with green salad,I dont have any underlying decease