Hi anshul2014,
I'm hoping that you can provide a bit more information on what you've done so far, since it sounds like you've used a lot of questions already:
1) How long have you been studying?
2) What materials have you used?
3) Have you taken the GMAT? If so, then what were your scores?
4) What is your goal score?
5) When are you planning to take the GMAT?
While it might be tempting to do lots of practice problems, you have to learn the various methods and tactics to approach the GMAT in an effective way. If your goal is to improve your GMAT score, then you might have to learn a new way of approaching the entire process of studying for the Test (as opposed to just doing more practice problems in the same ways that you did before).
GMAT assassins aren't born, they're made,
Rich