pain in your left rib cage could be gastritis or related to your rib cage muscles or heart related. i would suggest you to get your heart checked..maybe get an ecg done and start treatment for gastritis.
diarrhoea could be due to infection or gastritis. drink plent of water and use ORS when you have severe diarrhoea. you might want to see a gastroenterologist to rule out lactose intolerance and other intestine related infection or conditions.
Health Tips
The following lifestyle changes could help: - 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 - Increase daily intake of water to 3liters - Avoid/Stop smoking and drinking - Reduce stress through methods such as yoga/meditation. - Avoid painkillers as it will increase your gastric problems at this moment.