Don't focus so much on the magical number that people seem to think 700 is. It's not. A 680 would still be competitive at most schools.

I think you need to clear your head (go for a run, have a drink with friends, see a stupid movie), then regroup.

Take a brief break from taking timed practice tests and spend the next few days pounding through practice questions in the Official Guide, especially in quant. Take advantage of the forums here to get help on specific problems. If you really can't crack it, then delay your test and work with a tutor. A low 600s score will hurt more than the rescheduling fee.

Plan to take at least two more practice tests in the next 12 days, but I wouldn't take more than three. You'll tire yourself out. If you're done with MGMAT and GMATPrep, do the Princeton Review tests. They are adaptive like the real test and the answer explanations might help you finally crack the quant and see where you're going wrong.

Hope this helps!

Thanks a lot Spence, some very insightful advice!

I've since rescheduled my test because I realized that MGMAT scores are a little inflated, I scored 650, 650, 670, 680, 680, 700 on my MGMAT scored but only managed to get a measly 610 and 620 on GMAT prep and Powerprep respectively. MGMAT gave me a false sense of security, I thought I was doing well. Their materials and examples are extremely good, and they do a good job of explaining, but I feel that their scoring algorithm is way off.

I've since rescheduled my test because I realized that MGMAT scores are a little inflated, I scored 650, 650, 670, 680, 680, 700 on my MGMAT scored but only managed to get a measly 610 and 620 on GMAT prep and Powerprep respectively. MGMAT gave me a false sense of security, I thought I was doing well. Their materials and examples are extremely good, and they do a good job of explaining, but I feel that their scoring algorithm is way off.