Hi
Welcome to the MedHelp forum!
Commonest cause of chronic nausea is acidity. Take omeprazole (empty stomach in morning) along with antacid gel and see if it helps. Liver and kidney dysfunction is another cause. Hence kidney and liver function tests should be done. Other causes are diabetes and hypothyroidism. Electrolyte imbalance too can cause nausea. IBS, gluten or lactose intolerance, parasites in gut too can be the cause. A stool test should be done for worms, giardiasis etc. Also if nothing is found then food challenge test to detect food intolerance should be done.
Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!
I'm not a doctor, but one of my friends experiences similiar things. She found out she had a few food allergies. They were mild enough to not cause serious harm, yet they were strong enough to make her naucious. Maybe ask your doctor to run some allergy tests? Maybe you have a gluten or lactose allergy.