I have been having stomach pains, extreme stomach tenderness, nasuea, I did have ribbon-like stools that...?

turned into nothing but a mucus coming out of my bowels. I have lost 7 lbs in the past week. I went to the ER, they did several blood tests and X-rays, which showed no obstructions. The ER Dr. referred me to a Gastroenterologist who he said will probably do a barium enema on me. My questions are 1) Has anyone ever had this problem, if so...what may it be? 2) I have no insurance, approx. how much may a barium enema cost me?