Hi Joy,
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 (the 2 free CATs, and each of the 2 that come with Exam Pack 1 and Exam Pack 2), so it would be useful to know how you performed on one of those CATS. Once you have that score result, you should post back here and we can talk through what that score means
Beyond that point, many Test Takers spend 3 months (or more) of consistent study time before they hit their 'peak' scores, so the fact that you've spent just 3 weeks on your studies will likely impact how well you perform on the Official GMAT. Depending on your goals, you might want to consider pushing back your Test Date.
1) What study materials have you used so far?
2) What is your goal score?
3) When are you planning to apply to Business School?
4) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich