Gastric burning, heartburn and bloating
(if this is what you say hard stomach
) are symptoms of gastritis or gastric/duodenal ulcer.
It will help, if you avoid anything acidic; vinegar, fruits, also alcohol, aspirins, vit C, ibuprofen, and if you limit heavy protein/fatty foods, what in general is animal food.
You may want to order a test for H. pylori, which is the most common cause of chronic gastritis.