Having gas in my stomach and it's causing pain in left side of stomach. what should i do?

See ur doctor: "gas pains" can also be symptoms of other treatable causes such as ulcers, poor stomach emptying, hernias, poor biting (ill-fitting dentures or malocclusion of teeth), gut allergies (not necessarily manifest by hives), pancreas or gall bodden problems, etc - if persistent would recommend seeing ur doctor, even if initially responding to antacids/simethicone/anti-gas charcoal, or omeprazole