Hello Metformine is one most potent and effective antidiabetic drug . Its side effects are nausea, burping , flatulence , indigestion , abdominal discomfort , diarrhea , headache , lightheadedness , anorexia . Since you are taking nexium , so this is also good . But do as these measures . Try raising the head of your be about 4 inches with blocks. It might also help to avoid drinking or eating for 2 hours before you lie down . Avoid fatty , greasy , oily , spicy foods . When such patient visit I advise them to take antacid ( oxetacin with in it ) . Some enzyme preparation also helps . If possible reduce the dose and adjust , as it will take some time to drug to adjust in body. Hope this will help you.