Hi roro555,
Most Test Takers spend 3 months (or more) on their studies to hit their 'peak' scores, so you're still relatively early on in your studies.
That having been said, your CAT scores are all 'clustered' in the high-500s which means that you're dealing with each CAT in the same general way. Most Test Takers who take a 'book-heavy' study approach tend to get 'stuck' at a certain scoring level. It might be too early to say for sure that that is what's happening here, but there's certainly some evidence of it. As such, your next few weeks of study should be focused on tactics and making improvements to how you do your work.
If in the next couple of weeks your scores are still in this same general range, then some larger adjustments will have to be made.
When are you planning to take the GMAT?
When are you planning to apply to Business School?
GMAT assassins aren't born they're made,
Rich