I'd also remove things like gluten, dairy, coffee, tea and see if that helps. Maybe try something like nexium or prilosec too
Thanks for response:-) the thing is i used not to have allergy on food and I have been very careful to the food I eat: no spicy no rice no smoking and drinking(only drink water and juice sometime).
while gastritis can cause nausea, you need to find the cause of the gastritis. something is irritating the lining of your stomach, my guess would be something you are eating on a regular basis.
I'd suggest getting tested for food allergies and try eating a bland diet that elminates irritating foods like gluten, dairy, greasy food, etc.