recent colonoscopy experience

I had my first colonoscopy last Friday. I am 46 and my mother has had two surgeries for colon CA, so I felt pretty good about being so responsible. I went to every website I could find and researched all aspects of the procedure (patient teaching, videos of colonoscopies, personal experiences, etc.) I also spoke to several people who had gone through the procedure recently including my husband and my OB/GYN. I felt very well informed and more than educated about what would happen, what I would see on the screen, and how it would feel.
I was given Versed 2 mg and Demerol 50 mg IVP and the doctor waited until I assured him that I was groggy. Everythiing went just as I expected until just after insertion when air was instilled into my colon. I experienced some of the worst pain I have ever felt. The doctor immediately instructed the nurse to give me "25 more" which I assumed meant more Demerol. He continued the exam with me moaning in pain. I felt every mm. of my colon being blown up and navigated. I tried to watch the screen because I was really interested to see my own colon after viewing so many others in my preparation for the procedure. The pain was practically unbearable. Since then, I have had trouble concentrating and sleeping because I keep reliving this scene. I feel so duped and betrayed. All of the instructions and testimonials I read stated that there is little dicomfort and the Versed gives the patient amnesia to any discomfort that may occur. I have lamazed three children and had I known ahead of time, I would have gotten into a breathing pattern and anticipated the pain. I will know better next time. And as a nurse, I will return in 5 years because of my FH.
I guess what I want from you guys is some validation that indeed this does occur occasionally and that I'm not alone in this experience.
Thanks for your input. Sorry about the length of this, but I needed to vent!