What should I expect at my colonoscopy?

I'm having a colonoscopy next week and I'm scared. I've had conscious sedation before (they said they're giving me an IV which I've had non-IV consious sedation and I fell asleep so I'm uming that's a good sign) and I don't remember a thing. I don't want it to hurt--during or after. I HAVE to have it. My brother had polyps removed at 16, my grandfather had one every year to have polyps removed, and both of his sisters had colon cancer so it's important that I have this done (I'm going to be 30 on Thursday). I have trauma issues so I'm really scared. My psych doc said she would sedate before hand and I think I might do this. What should I expect? They didn't give me much info except for a brochure. Thanks ahead of time.