Hello thank you for your query. The period like cramping is indicative of an imminent labour as you are near term Some amount of heartburn and vomiting is common in pregnancy, particularly during the first trimester. However, what you describe sounds pretty severe. Continue taking the antacids. have very small, but frequent meals. Try surviving more on liquids. Avoid an oily or spicy diet - stick to bland, semi solid foods. Make sure you are not overmedicated, as medicines can lead to gastritis. The symptoms should regress after delivery, hwoever if they dont, please consult a gastroenterologist and consider an endoscopy for diagnosis. Take care.