My son who is 11 has been on extensive antibiotics for many strep infections. He had tonsillectomy on 12/30. He has extreme belly pain and diarrhea. All blood work Dr has drawn has returned negative along with neg. Cat scan. He stresses at school about having diarrhea and abdomen pain which makes the symptoms worse. He doesn t like to go anywhere now unless he knows there is a bathrrom. Any further avenues you can suggest?