General Anesthesia?!?

Well, I am 13 years old and have to have an endoscopy procedure done in about 3 weeks. I am terrified of going 'under'... I was just wondering if you can dream when you are under. And if you have any sense of time.. I have done a little 'research' and people are saying it feels like you go under and then immediately are awoken. Will that be in the same effect if the procedure is 15 to 30 mintues? Also, I had to be put under when I was about 5 for a cat scan. If I didn't get sick (throw up) after awakening then, does that mean I have a good chance of not getting sick this time? Does everyone get sick? Im sorry I know I have a lot of questions.. just a little uneasy with the subject I guess.. thanks for any answers!!