Hi anirudhrao,
I'm sorry to hear that Test Day didn't go as well as hoped. There are a variety of factors that can influence your performance on your practice CATs/mocks - including the "brand" of CAT that you took, the time of day you take your test, how well-rested you were, the environment that you took the test in, etc.).
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. By taking a CAT just 3 days your Official GMAT, there's a reasonable chance that you were a little too tired on Test Day to perform better.
Beyond all of those considerations, when these types of score drops occur, the two likely "causes" involve either something that was unrealistic during practice or something that was surprising (or not accounted for) on Test Day. Before we discuss any of those potential issues though, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) What were your Quant and Verbal Scaled Scores on your Official GMAT?
2) How long have you studied in total? How many hours do you typically study each week?
3) What study materials have you used so far?
4) On what dates (or approximate 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)?
Goals:
5) What is your overall goal score?
6) When are you planning to apply to Business School and what Schools are you planning to apply to?
If you took your GMAT at a Test Center, then you might also choose to purchase the Enhanced Score Report. 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 on Test Day (and what you should work on to score higher). If you purchase the ESR, then I'll be happy to analyze it for you.
GMAT assassins aren't born, they're made,
Rich