Week 2 of diarrhea!!!

So I've had my J-tube for severe gastroparesis since july 2nd, then 2 weeks ago I started getting severe liquid diarrhea, my gi dr. treated it w/ xifacin as a bacteria overgrowth in my gi tract, it kind of slowed down some what last week, and now this week is back with full force (today i finally feel like i'm really getting dehydrated) I called my gi dr's nurse and she talked to the doctor and said it sounds like i'm losing ground w this, I stopped my j-tube feedings for 2 nights in a row (the last 2 nights) and started the antibiotic again, and am taking the max Immodium ad dose. They ordered stool studdies today and then want me to have a colonoscopy set up for monday morning, meanwhile i am sipping on gatorade which I can't stand the taste of. Atleast w/ my GP i had abdominal pain and vomiting non stop, but this I really don't have cramps or anything, it's just moving thru so fast and I don't even know what it is because I didn't feed for 48hrs. I hope these tests reveal something but the prep for the colonoscopy doesn't thrill me at all especially since pure liquidy stools is my problemin the first place. Does anyone know what htis might be or what may be causing it????