Hi mayankgupta01,
First off, a 660/Q50 is a strong score (it's right around the 80th percentile overall), so it could be enough to get you into your first-choice School. As such, a retest might not be necessary.
1) What Schools are you planning to apply to?
2) When are you planning to apply?
From what you've described, you used a 'book-heavy' study approach; many Test Takers who study in this way end up getting 'stuck' at a particular scoring level and that is likely what has happened to you. If you do decide to retest, then you'll probably benefit from investing in some non-book resources and learning/practicing some new Tactics.
GMAT assassins aren't born, they're made,
Rich