1. Don't use Princeton Review
. Also, don't trust their CATs as representative of exam performance.
2. Study MGMAT in depth. All books. Even if you find things very basic and elementary, don't skip it as you mentioned you did in your studies. Read everything and do all problems.
3. REVIEW your mistakes. Why are you getting things wrong? Speed? Understanding? Both? You can learn a lot from using an error log
. And make sure to go back and UNDERSTAND the underlying concept of the questions you got wrong.
4. Calm down a little.
This is not an SOS moment. Also you don't need to feel "devastated" or feel like you are under "tremendous pressure." If you were scoring well under non-testing conditions, you need to calm down and go into your practice tests with that same mindset.
5. Maybe a prep course?