Talk to Pediatric Gastroenterologist on Severe Abdominal Pain And Bloating

My 7 years old son experiencing severe bloating and abdominal pain from last 3 months. Blood test, urine test, x ray , ultrasounnd , poo test , gluten lactose tests are all clear. But whatever he eats it causes bloating and pain, sometimes even without eating anything he got hard tummy and pain. 2 years ago he had constipation but it was settled a year ago, now he opening his bowl regularly but still have abdominal pain. He is taking gluten free , lactose free food from last month but no improvement. He is eating mainly chicken fish rice, banana , cocumber. We are in australia and doctors are unable to identify issue in 3 months. We are also thinking to go Pakistan for check up. Please advice the possible issues based on attached reports and above symptoms.