First, you should ask yourself why you are taking so many practice tests?
The goal here is not to speed through as many tests as possible - but rather to learn from your mistakes and to understand the various types of questions you might see so you are prepared when you do see them.
Give an honest effort in reviewing your mistakes and identifying potential patterns in your mistakes. Then review the fundamentals related to those problem areas.
Mental fatigue is something that you will need to address during the test. If you continue going through all these questions without actually recognizing your mistakes, then you will be exhausted by the time of your actual exam and score even lower.
Give yourself a break - review your mistakes religiously in various orders - forwards, backwards, etc. Then retest yourself.
When you get to that stage, you may look at our practice test: http://www.gmatpill.com/gmat-practice-t ... promo=free
... and more
What's Inside GMAT Pill?
Zeke Lee, GMAT Pill Study Method (Study Less. Score More.)
GMAT Pill Reviews | GMAT PILL Free Practice Test