Hello! Thank you for the query. Gastroscopy and barium swallow test are good for upper digestive tract diagnostics. Your pain is in the lower left side and it seems no test has been done to check this part of your bowels. Lower left side abdominal pain and bowels problems are most likely caused by large intestine disease called diverticulitis. This condition is caused by chronic constipation. Due to increased pressure in the large intestine some kind of pouches are created in the intestinal wall. This pouches are weak, part of stool can stuck in it what leads to an inflammation. Inflammation of such diverticle can cause serious intestine perforation. That is why I suggest you to visit gastroenterologist. You should have checked if there is an acute inflammation right now (CRP and WBC level will be elevated and pain present). If there an inflammation, antibiotic course and mild diet should be ordered. After healing acute inflammation or in case of lack of it, colonoscopy should be definitely done. If you will be diagnosed with diverticles and the pain will be coming back, surgery should be considered. In a meanwhile please increase fiber rich products, mineral water intake and physical activity. Hope this will help. Regards.