Hi aanchals,
A CAT is really a 'measuring device' - when used correctly, it will give you a realistic score and help define your strengths and weaknesses, but it will NOT help you to fix any of those weaknesses. To raise your scores, you have to learn the necessary Tactics and put in the proper practice and repetitions. The CAT will show you whether your studies are helping you to improve or not. In addition, the process of taking (and reviewing) a CAT requires a significant amount of energy and effort - and takes time to 'recover' from. This is one of the reasons why you typically should not take more than 1 CAT per week - and your last CAT should be taken about 1 week before Test Day.
While the most realistic CATs available are the 6 from GMAC, retaking a CAT that you've already taken is NOT a realistic way to assess your skills - since you will likely see some 'repeat' questions that you have already faced. Unfortunately, seeing even a couple of repeats can 'throw off' the Scoring Algorithm and impact your pacing, energy levels, fatigue, etc. (meaning that they would likely all appear to be better than they actually are).
Based on your timeframe and current Test Date, you shouldn't take more than 2 additional CATs. If you're consistently scoring around 630 though, then you will likely need far more than 2 weeks of additional study time before you can get to the point that you are consistently core 720+. By extension, you might want to consider pushing back your Test Date.
Before I can offer you the specific advice that you’re looking for, it would help if you could provide a bit more information on how you've been studying and your goals:
1) How long have you studied? How many hours do you typically study each week?
2) What study materials have you used so far?
3) 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)?
4) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich