There are many viral and bacterial causes of Gastritis and Gastroenteritis ("stomach flu"). Vomiting from viral gastritis usually stops in 12 to 48 hours. If diarrhea is present, it usually continues for several days.
Gastritis may be acute or chronic. Sudden, severe inflammation of the stomach lining is called acute gastritis. Inflammation that lasts for a long time is called chronic gastritis. If chronic gastritis is not treated, it may last for years or even a lifetime.
Have you been checked for Helicobacter pylori (H. pylori) ? This is a bacterium that causes chronic inflammation of the inner lining of the stomach (gastritis) in humans. This bacterium also is considered as a common cause of ulcers worldwide; as many as 90% of people with ulcers have detectable organisms.
Do make an appointment if your symptoms continue and know that a GI doctor specializes in problems with the digestive tract - I cannot tell you what this person will do other than to say - most likely some testing.
I am glad you found us as this is a great forum and place to talk with others who share many of the same problems as you do.
and Heart/Cardiovascular Disease. "She Stood in the Storm & When the Wind Did Not Blow Her Away, She Adjusted Her Sails."