Hi felixduan320,
At most Test Facilities, the laminated pad that you will receive is 'legal-pad sized', so there's a lot of surface area for you to write on. That having been said, if you need a new pad at any point during the Exam, you can ask for one. Most of the Testing Labs have just one Moderator though - and if that person is helping someone else (or that person takes a few seconds to notice that your hand is raised), then you might need to wait a short amount of time to receive a new pad.
To minimize the impact of these types of potential delays, you should plan to exchange your pad during each of the two 8-minute breaks (just take it with you when you leave the Lab, give it to the Moderator and ask for a new one when you re-enter).
Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) What study materials have you used so far?
2) On what dates did you take EACH of your CATs/mocks and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
3) What is your overall goal score?
4) When are you planning to take the GMAT?
GMAT assassins aren't born, they're made,
Rich