As has been advised, you need to get him to a Gastroenterologist asap. But, don't jump the gun, there is alot of other things that it could be before assuming that it's Crohn's or Colitis.
It could be gastroenteritis, Celiac, Lactose intolerance, parasite, infection. Hopefully it's not Crohn's but you need to get some diagnostics done soon so you know one way or the other what's going on.
All of us here know all to well how difficult the waiting game is. I guess that's why they call us patients. As tough as it can be, try to be strong and positive for you son's sake.
Please post an update as soon as you find out what's going on.