Anus Pain

Ok, I'm not sure where to post this, but hopefully I'm in the right spot.  My 3 1/2 yr old son started screaming in the middle of the night on Saturday that his butt hurts.  It is the actual anus that hurts.  I called the pediatrician last night because it hasn't gotten any better and he sent us directly to the ER to be seen and get some cultures.  The ER did a culture...although it was from his underwear that was placed in the trash by a nurse.  That was his first time for diarrhea during all of this.  The hospital sent us home after getting the stool and urine sample.  
His diarrhea has some form to some of it and mucus for the rest.  It is brown, but with a hint of yellow and smells like a dirty hamster cage...or a pig pen as my husband says.  He has explosive gas with this as well.  He recently started saying the his tummy hurts too.  I have worked in healthcare and have seen and smelled C-Diff...however it has been a while so I don't really remember the smell.  
C-Diff is the only thing I know of in the bowel that causes this type of stuff.  My main question is, what can I do to help him?  He just screams that it hurts and I can't do anything about it.  The pain comes and goes.  What else could this be?
Thanks,
Marjorie

[boron]

If it is C-Diff, the test will show, also if is it Rotavirus, or bacteria or parasites from food poisoning.

It's hard to say anything before test results.

Pale stool comes from malabsorption of fats (many reasons). Pale, sticky, foamy, foul smelling stool is characteristic.
Mucus is in shigellosis, in IBD...

If his anus is burning, there is one anestetic or analgesic ointment , it may bring some relief.
Don't give him FATTY food, milk, sweets, fruits, vegetables until diarrhea lasts. He should DRINK (water, tea, or solutions like Pedialyte).