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During the first meal the stomach is empty and the symptom you are telling is due to acidity or even gastritis
which may be causing you to throw up.Please take antacid
like ranitidine-300 mg and if required for nausea
you can take domperidone
10mg.Both 1 tablets each before every meal three times a day for 1 week then you can reduce for 2 times a day and continue for 2 weeks and the problem will settle.