May be you're already aware of this but in case you aren't:
On the mgmat website, there is a tool that generates an assessment summary of your performance across exams. With that, it's easy to identify your weak areas. You can also generate assessments for each exam and export them. If you do a side by side comparisons of the exams, it should tell you why your scores are inconsistent.

Make sure that you know WHY you make a given decision when eliminating an answer choice or choosing the correct one. Don't rush. Do one test per two days and on the remaining days practice questions froom the verbal section. Make a list of question types you find more challenging and focus on becoming more familiar with them. Focus on timing during the tests but concentrate on quality and ignore timing when you are learning.