Causes of excess gas in the digestive tract are swallowed air, breakdown of undigested foods, lactose intolerance and malabsorption of certain foods. It is likely that you have gastritis which is causing malabsorption and hence the gas. If you have a doubt about your kidney status, I would advise you to do a renal function tests in which you can confirm the status of your kidneys. The following steps will help with your current condition: - Don't skip meals, you may not feel like eating but in such conditions you should have the reduced amount in frequent intervals(i.e. 3 square meals broken down to 5 or 6 as you can tolerate) and slowly increase as you get better. - Reduce/ Avoid spicy,fried, fatty, junk and oily food - Avoid/ Limit drinking coffee, tea and carbonated drinks to once a day - Exercise regularly (minimum 30-45mins/day) - Increase daily intake of water to 3 liters - Avoid/Stop smoking and drinking if you have the habit - Reduce stress through methods such as yoga/meditation. - Avoid painkillers as it will increase your gastric problems at this moment.