I had an unsedated sigmoidoscopy and it was one of the most painful things I have ever experienced. I will NEVER ever do that again.
I had a couple of these and omg, I had the worst experiences. I couldn't handle the pain level at all, of course I was flaring severely and everything was uncomfortable. I kept feeling the urge too, literally jumped a few times.
Once I woke up during a scope. That was also a bad experience.
I've seen people here say they've done it unsedated though, and it was ok.