Hi MW18,
GMAC has publicly stated that the Official Score that you earn on Test Day is within +/- 30 points of actual ability. Based on your 3 Official GMAT Scores, those results show that you essentially performed the same way each time (about a 460 +/- a few points). Regardless of how you have studied for each attempt, you appear to perform the same general way every time you take the Official GMAT. Thus, if you continue to study in the same ways as before, it's likely that you'll continue to score in the high-400s.
Since you've noted that you're scoring higher in your CATs, we need to define HOW you took those practice Exams.
When you took your CATs:
1) Did you take the ENTIRE CAT each time (including the Essay and IR sections)?
2) Did you take them at home?
3) Did you take them at the same time of day as when you plan to take your Official GMAT?
4) Did you ever do ANYTHING during your CATs that you couldn't do on Test Day (pause the CAT, skip sections, take longer breaks, etc.)?
5) Did you ever take a CAT more than once? Had you seen any of the questions BEFORE?
Beyond those questions, I'd like to know a bit more about your timeline and goals:
1) Is your goal score 550 or something else?
2) When are you planning to apply to Business School?
3) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich