Hi prateetchhatwal,
To start, the 750+ score is approximately the 98th percentile - meaning that 98% of Test Takers never score that high (regardless of how long they study or the number of times that they take the GMAT). Thankfully, NO Business School requires a score that high - so it's important to realize that the score that you "want" and the score that you "need" are not the same thing.
Raising a 540 to a 750+ will likely take at least another 3 months of consistent, guided study - and you'll have to make significant improvements to how you handle BOTH the Quant and Verbal sections. A March 8th Test Date gives you just about 6.5 weeks of study time though, so you might need to consider pushing back your Test Date.
1) When did you take this CAT?
2) Going forward, how many hours do you think you can consistently study each week?
GMAT assassins aren't born, they're made,
Rich