Have you considered changing your diet? Also, you may want to think about ingesting more probiotics. Kefir is a wonderful source, there is plenty about it on the internet if you're not familiar with it.
I too have nausea much of the time with a burning belly, and am trying this myself. it wouldn't hurt to try it. The positive effects of probiotics may take a few weeks.
Do you have any other symptoms? dizzy? My son has been diagnosed with POTS. His main symptom is nausea,(he has constipation instead of diarrhea). He has also had every gastro test under the sun) His doctors have ruled out the nausea being from anything gastro related.
They believe his is neurological. The POTS (postural orthostatic tachycardia syndrome or autonomic dysfunction) has a long list of possible symptoms.
Ive been suffering from terrible nausea, stomach pains, lightheadedness, constipation and fatigue for more than a year. I had lots of tests inc ct scan, ultrasound scan, x ray and endoscopy. The only thing that showed up was mild gastritis and a stomach polyp for which they took a biopsy and that was ok. Ive tried everything to combat the nausea cos I find it really affects my life, I never want to go out anywhere cos Im afraid I'll be sick. Ive also lost weight because Id lost my appetite. Have tried various things such as travel sickness tablets, seabands(for your wrist), chrystallised ginger (from a health food store) as well as domperidone from my doctor. Sometimes it helps sometimes not! A recent blood test unexpectantly showed I had pernicious anemia, for which Ive just had a course of B12 injections. I will need to be on these for life. Ive read online that pernicious anemia is an autoimmune disorder which can lead to stomach problems and nausea so perhaps you should get your dr to check your blood for this. Hope you feel better soon - nausea is a really unpleasant feeling