I agree. Calm down. You MUST take this procedure to find out what is wrong. I'm not an authority on the subject I accept, but I honestly feel that the writer who had the awful Sigmoid procedure had an awful PRACTITIONER rather than an awful PROCEDURE. My elderly mother just recently had a sigmoidoscopy and as pattiecake says, was in lala land and was absolutley fine. They assessed and dealt with her problems and she's well on the road to recovery now and is fitter than she has been in years as a result.
Find a friend who can go with you and support you on the day. Tell your doctor how freaked out you are - it's his/her job to help you understand the reality of this procedure and how they are going to help you be calm throughout. They might even decide to give you an extra dose of "lala juice" to help calm you more than usual. I'm absolutley guessing here....and so are you until you talk to your doctor and get him/her to put your mind at rest. Try and do it as soon as possible or you are going to just be a mess.
I'd even go so far as to say that if they don't put your mind at rest, change your doctor. But do NOT duck out of the procedure, it is too important. Seriously.
It is NOTHING like being raped, I promise. Get this out of your head right now and make an appointment to see your doctor. TODAY.