On and off Vomiting and Diarrhea

My son has had 4 distinct bouts with vomiting and diarrhea since Nov. 2nd. He gets better for 5-6 days and has another bout. This last bout occurred on 11/19 and was so severe he couldn't leave the bathroom for 4 hrs. until he was vomiting bile and had nothing left in him. The Dr.s office referred me to a GI doc. but we can't be seen until Dec. 11. He is only 6 yrs. old. Blood work from his last bout came back and said he did not suffer from Crohn's or Celiac disease. I'm at my wits end. I've changed his toothbrush twice, am cleaning like a freak, and my other children are staying healthy. Any ideas from anyone who has perhaps heard of this happening to someone else??