Hi taniad,
To start, regardless of how you choose to study going forward, it's important to remember that Test Day is a rather specific 'event' - the details are specific and they matter, so you have to train as best as you can for all of them. The more realistic you can make your CATs/mocks, the more likely the score results are to be accurate. The more you deviate, the more "inflated" your practice scores can become. When you take CATs in the future, it's important that you take each one in a realistic fashion (take the FULL CAT - with the Essay and IR sections, take it away from your home, at the same time of day as when you'll take the Official GMAT, etc.).
The scoring algorithm on the Official GMAT is far more complicated than most people realize. Since that algorithm is proprietary, no GMAT company has an exact match for it, thus CAT scores can vary a bit based on the 'biases' involved in their respective designs. The most realistic CATs available are the 6 from GMAC, but retaking a CAT that you've already taken is NOT a realistic way to assess your skills. Seeing even a few 'repeat' questions can 'throw off' the Scoring Algorithm and impact your pacing, energy levels, fatigue, etc. (meaning that they would likely all be better than they normally would be). Thankfully, the CATs from Kaplan,
MGMAT and Veritas are all 'close enough' to the real thing that they will provide you with a relatively realistic score assessment (assuming that you use the CAT correctly).
You might choose to purchase the Enhanced Score Report. While the ESR doesn't provide a lot of information, there are usually a few data points that we can use to define what went wrong (and what you should work on to score higher). If you purchase the ESR, then I'll be happy to analyze it for you.
1) What is the latest that you can take the Official GMAT?
2) Going forward, how many hours do you think you can consistently study each week?
GMAT assassins aren't born, they're made,
Rich