Thanks for your question on Health Care Magic.
I can understand your situation and problem.
Feeling of bubbles in left side of chest is commonly due to either
gastritis or due to
arrhythmia.
Since you had history of atrial
fibrillation, better to first rule out arrhythmia in your case.
So get done ecg, 2d echo and Holter monitoring (24 hour continuous monitoring of ecg).
If all these are normal than no need to worry for atrial fibrillation or arrhythmia.
Gastritis can cause gaseous distention of stomach and this can give bubble feeling in chest.
So take
proton pump inhibitors. Avoid
stress and tension. Avoid hot and spicy food. Avoid large meals, instead take frequent small meals.
Don't worry, you will be alright. But first rule out arrhythmia.
Hope I have solved your query.
Wish you good health. Thanks