Recurring abdominal pain approx. every other month, have tested positive for strep in the past

My 13 year old son as been experiencing centralized abdominal pain that lasts 3 - 5 days and occurs approximately every other month. He has been tested twice for Celiac which came back negative. His CBC and Lipase has also come back normal. Occiasionally he has nausea and fever accompanying the pain. He has tested positive twice now for strep. He has been tested and come back negative, but with same symptoms as when positive. Is it possble to have chonic strep and go for weeks without showing symptoms? He rearely has the sore throat. His pediatrician wants him to see a GI doctor but with all the blood tests coming back normal, I'm unsure.