Any guesses to what this could be?

I am a 20 year old female. I have had digestive symptoms for months.
I have frequent bowel movements (7+ times per day), most of which are diarrhea or extremely loose. Anti-diarrheal medications do not work; the only thing that "works" to solidify my stool is Vicodin, but this constipates me, which doesn't help either.
My stool contains a great deal of undigested food - vegetables (lettuce, tomato, etc), meat, grain (rice cereal, etc.).
I have severe abdominal distension.
I have sharp pains throughout my abdomen constantly.
My stool is usually extremely fatty, foamy, and foul-smelling.
Nearly every bowel movement is painful.
I am nauseous daily. I never know if I will be able to keep down food. Accompanying food with milk seems to ease the nausea.
My weight fluctuates extremely. My typical weight is 140 (I am 5'11") and it drops down to 125 and back up within a week or two.
This is accompanied by many other symptoms - joint pain, extreme fatigue, chest pain, heart palpitations, inability to control body temperature (alternating quickly between sweating and shaking with cold chills), muscle weakness, hand tremors, hypoglycemia, low blood pressure, blurred/distorted vision, memory loss, confusion, frequent urination, near-daily low-grade fevers, constant headache.

I have seen an internist, a gastroenterologist, and a gynecologist.
In May, I went in for surgery to remove a ruptured ovarian cyst, at which point they also noticed appendicitis and removed my appendix. The biopsy of my appendix returned somewhat normal, except they had found multiple stones and stool within the appendix, but said it seemed normal.

During a follow-up gynecologic exam, my doctor did an ultrasound due to my abdominal distension, and saw that my large intestine was in between my uterus and my bladder.

I have since had a colonoscopy, an endoscopy, a great deal of bloodwork (vitamin levels, ANA, CSR, RA,H.pylori, liver and kidney panels, CBC) an EKG, and a stool study to test for bacteria and parasites.

All of these tests have come back clean/negative.

What do I do next? My doctors are literally guessing. I'm currently taking meclizine, in the off chance that I may have an inner ear infection that they can't see? The medicine is not helping.
They have not given me any more medicine.
I am completely lost, and constantly miserable. Any advice would be appreciated.