Check into low stomach acidity which can give the same symptoms or acid reflux - taking nexium further blocks acid which is critical to digest food and keep pathogens at bay - if you have dysbiosis (including candida) it may be due incorrect amounts of digestive juices (stomach acid, bile, pancreatic enzymes).
If you truly have excess acid ( most people have the opposite and are treated as they have excess) you may want to check for hiatial hernia which can cause the acid to escape into the esophagus and burn (even though theres no excess acid)
Mike