Hello Welcome to health care magic. Stomach ache with excessive sweating can be because of peptic ulcer/urinary colic/appendicitis. You have not mentioned in which part of abdomen you get the pain. If the pain is in upper abdomen,comes on eating and is of burning type it can be due to gastric ulcer. It can be treated with PPIs like omeprazole taken once a day for atleast a month.Further management with detailed investigation like upper GI endoscopy with consultation of gastroenterologist can be considered if necessary. Non NSAIDs option like tramadol can be opted instead of ibuprofen for the sciatica pain. Also avoid eating hot,spicy food,alcohol and caffeinated drinks which may increase this type of pain. Maintain adequate body hydration. If pain is in lower abdomen and is cyclical ,it can be due to other possibilities mentioned.In that case you will need physical examination by general surgeon and USG abdo.Further management depends upon diagnosis. Hope I answered your query. Wish you good health.