My question is directed to a health care professional?

I am scheduled for a virtual colonoscopy tomorrow morning. I have had two unsuccessful colonoscopies due to not being fully evacuated. I was put on prednisone and ascotol for 2 months due to a very highly inflamed colon and ulcerative colitis. The Dr. told me that I have a twisted colon, and scar tissue probably due to a complete hysterectomy in 2000. I took citrate of magnesia, alot of water, before the first procedure, with, as I said not sufficient results. Second one, I asked for something other than citrate of magnesia, the Dr. prescribed 36 (if i remember correctly) pills, they did,nt work either. I now was given-three small bottles of Tagitol-started at 8:00 this morning-then drank alot of water-after that it was a bottle of citric of magnesia- and 4 little pills (the name escapes me)-I have not had a bowel movement as yet. I was also given a suppository to be inserted 2 hrs. before my 8:30 procedure. They are not in the office, as it is Sunday. I don't know what to do. I did tell the nurse about the problems that i previously had-she told me to just follow the directions, and I should,nt have any problems. I just drank 2 hot cups of clear hot broth-more water, but it's all been to no avail. I can't go through this anymore. I hear of so many people who go through colonoscopies without any problems whatsoever. I am at my wits end-I,m tired and totally disgusted, what if anything can I do? any suggestions would be very appreciated.