Presence of antibodies suggests the person is either recovered from infection or he or she is vaccinated. So don't worry. You don't have covid infection as of now.
Secondly, covid itself doesn't cause acidity. However too many antibiotics or drugs during covid treatment may cause gastric upset and acidity.
Next Steps
You need to stop worrying about Covid. for acidity take tab Pantoprazol 40 before food for 3 days. You can also take Antacid syrup for acidity. Acidity should not last longer