Sedation with Versed and fentanyl - should I cancel?

My first colonoscopy is scheduled for next week, and I’m on the verge of canceling. My medical group only offers a versed/midazolam and fentanyl combo for the sedation. They don’t offer propofol.

I’m extremely worried because in the past, I’ve had a couple of dental procedures with “twilight” sedation that went horribly. Two years ago I had a full blown panic attack (crying, thrashing around) after I was given nitrous oxide for a cavity filling, so they gave me a Triazolam pill, which was supposed to sedate me. It didn’t work at all, so after an hour, they gave me two more pills (.75mg total). It made me feel woozy and heavy, but I remained fully conscious and remember the whole procedure, even though they swore I wouldn’t. It was awful. I had a very similar experience many years ago when I had my wisdom teeth pulled. Before that procedure they just gave me Valium/diazepam. I don’t know the dose. I still have nightmares about it.

So basically, I am terrified of twilight sedation, so I don’t think I want to do the colonoscopy with midazolam. I suspect benzodiazepines in general might be ineffective for me since triazolam and diazepam both failed to work like they were supposed to. I’ve also taken Ativan/lorazepam in the past and it had zero effect. Is this a thing? Are these meds just not effective for some people?

I don’t know what to do. I was referred by my PCP for the colonoscopy because I’ve had some bleeding and diarrhea. I feel like I need to do it, but I also don’t want to be traumatized. The clinic said the only way they’ll do general anesthesia is if I have a medical reason and if my insurance approves it, but I’m not sure if I have a case to make since I haven’t taken midazolam before. I don’t even necessarily want general anesthesia, but I want to be fully asleep.