I had the viral flu last week and now having bubbly like gut rot feeling in my upper stomach since a week and it seems to be getting worse?

GI flora imbalance. Gastroenteritis or the 'stomach flu' typical causes nausea and vomiting, as well as diarrhea. This can result in a loss of the natural levels of 'good bacteria' found in the stomach and intestines. And that can lead to excess gas production and altered bowel habits. To replenish these good bacteria, eat some 'probiotic food'. There are multiple brands of yogurt available that contain them.