When I was studying for the COMP, I used Uworld as well. Don't worry about doing questions on there because not only will it help you with the COMP but the more exposure you get to the same questions the better you will learn the material. Many people do uworld twice before taking the step so I wouldn't worry too much. And if you are really interested in doing completely new questions, you can always sign up for kaplan medical which, IMO, are just as good if not better than Uworld.
Ross Graduate- 2012
PGY1- Surgery Prelim