I'm so sorry to hear what happened to you. I completely understand why you fear the colonoscopy.
I don't know if this helps, but I don't remember my colonoscopies at all -- I was completely sedated for them. I told my doctor I wanted to be completely "out" and not remember a thing, and I don't remember anything from either of the two scopes I've had. They bring you into the procedure room, hook you up to an IV with the sedation drugs, and then you wake up in the recovery room.
I agree with whoever suggested asking for anxiety drugs to take the morning of the procedure and maybe the night before if you're really stressing out (xanax worked really well for me for severe claustrophobia when I had to fly recently for work). I do not think your doctor would have any problem prescribing these, and if he or she does, then find someone who is more compassionate.
I think therapy may be a good idea also.
Let us know how it goes.