Hi Stella85,
To start, a 660/Q45 is a solid score (it's right around the 80th percentile overall), so it could be enough to get you into your first-choice School. That having been said, GMAC has publicly stated that the Official Score that you earn on Test Day is within +/- 30 points of actual ability. Assuming a similar 'swing' in how your CATs function, your various score results show that you performed in the same range each time you took an Exam (680 +/- a few points) - and your Official Score is at the 'lower end' of your range.
If you're going to continue to study and retest, then it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) How long have you studied?
2) What study materials have you used so far?
3) When you took these CATs, did you take the FULL CAT each time (with the Essay and IR sections)?
Goals:
4) What is your goal score?
5) When are you planning to apply to Business School?
6) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich