Hi jiwen,
With a Q48/V38, you would not have ended up with a 660 (you'd have likely hit 690 or 700), so one (or more) of the numbers you've listed is incorrect. If you would like to know for sure, then you can order the Enhanced Score Report for this Exam. Depending on your Score Goal, you might want to order the ESR regardless. While the ESR doesn't provide a lot of information, there are usually a few data points that we can use to define what went wrong (and what you should work on to score higher). If you purchase the ESR, then I'll be happy to analyze it for you.
Beyond those issues, before I can offer you any advice on how you might better prepare for your next attempt, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) How did you score on your 1st Official GMAT?
2) How long did you study for each attempt?
3) What study materials have you used for each attempt?
4) How have you scored on EACH of your recent practice CATs (including the Quant and Verbal Scaled Scores for EACH)?
Goals:
5) What is your goal score?
6) When are you planning to apply to Business School?
7) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich