You can't take the scores too seriously as indicators, because they can vary naturally by 30-40 points even at the same level.
In order to tell if your studying is working, instead of focusing on the scores you're getting, ask yourself how you
feel while writing the practice CATs and going through the practice problems.
No, this isn't some touchy-feely theory. It's an indication of how confident you feel. When you see each question, can you immediately identify what's being asked and how to go about solving it, or are you still fumbling for a strategy? When you answer questions, are you most often confident that you've put the right answer? Or are you eliminating obvious wrong answers and then guessing? When you get the score, do you know 100% why you got the questions right that were right, and why you got the ones wrong that were wrong? Or are you still not sure? Do you truly understand the concepts, or are you just going for lucky guesses?
When you can answer all those questions with the answer that you're confident in your ability, then you'll be ready to write the test.