Hi Spyder,
Based on what you've described, there are 2 immediate 'issues' with how you chose to study:
1) Many Test Takers spend 3 months (or more) of consistent study time before they hit their 'peak' scores, so if you really studied for just 3 weeks, then it's likely that you just have not put in enough time and effort yet.
2) Each CAT is really just a 'measuring device' - when used correctly, it will give you a realistic score and help define your strengths and weaknesses, but it will NOT help you to fix any of those weaknesses. When used incorrectly, it will not give you a proper assessment (and might convince you that you're scoring at a higher level than you actually will on Test Day). To raise your scores, you have to put in the necessary practice and repetitions. The CAT will show you whether your studies are helping you to improve or not. As such, you really shouldn't take more than 1 FULL CAT per week. Taking 7 CATs in 3 weeks would not have been beneficial - and would have significantly 'eaten' into your actual study time.
1) What is your goal score?
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