Hi Achyut,
The situation that you're facing is one of the reasons why it's important to take CATs at regular intervals throughout your studies (and not waiting until the very end to take them) - there are aspects to scoring at a high level on the GMAT that you can learn ONLY by taking FULL-LENGTH CATs. It also looks like you did little work on the AWA section, which created a shorter overall Exam (and likely "inflated" your scores a bit).
Now you're down to your last week and some significant changes have to occur for you to hit 700+.
Based on the information that you provided, it looks like you rushed a bit through the Quant section. If you can slow down a bit and do a bit more work, you should be able to pick up a few points in that section. With a V28, you have at least 2 of the major categories (SC, RC and CR) in which you could be picking up some significant points, so some extra review and repetitions in those areas are warranted.
The harsh reality is that you're probably not going to improve 80+ points in 6 days. You should still take your GMAT as planned, and do your best, but if your goal is 700+ then you're going to probably end up studying more and taking the GMAT again.
GMAT assassins aren't born, they're made,
Rich