Nausea, recurrent vomiting and retching at night this comes with bloating and severe left sided abdominal pain. multiple blood tests all normal. irregular periods. normal pelvic & abdominal ultrasound. episodes last 8-10 hours & occur few weeks apart?

I recommend consulting a gastroenterologist despite the normal abdominal ultrasound.Although you don't mention bowel symptoms, Inflammatory bowel disease may still be present. If you've had previous abdominal surgery, intestinal adhesions would be a possibility. An occult hernia, impacted stool, intermittent intussusception,intermittent volvulus are rare & diverticulitis lasts longer than hours.