Hi abhic87,
From what you've described, you've uses a "book heavy" study approach so far. Even the best books are limited in what they can teach you; they also can't force you to approach questions in a certain way and their explanations are often one-sided. Given your score goal, you'll likely need to invest in some new, non-book resources and learn/practice some new Tactics.
You mentioned the score 'ranges' on your 3 CATs, but I'd like to know more about each of them individually:
1) What were the Overall Score and the Quant and Verbal Scaled Scores on each of your CATs?
2) Did you take the ENTIRE CAT each time (including the Essay and IR sections)?
3) Did you take them at home?
4) Did you take them at the same time of day as when you'll likely take your Official GMAT?
5) Did you ever do ANYTHING during your CATs that you couldn't do on Test Day (pause the CAT, skip sections, take longer breaks, etc.)?
6) Did you ever take a CAT more than once? Had you seen any of the questions before?
Thankfully, the GMAT is a predictable, standardized Test, so you CAN train to score at a higher level.
GMAT assassins aren't born, they're made,
Rich