I'm sorry you had a disappointing test experience. 690 is still a very good score - so I just want to congratulate on getting that high of a score (though I know you want a higher score!).
You don't mention what score you'd like to get. Can you let us know? Please also tell us what you did to prepare, including what materials you used, and what the results of your practice tests were. Please also indicate whether you took your practice tests under 100% official conditions (including essays); if you deviated from official conditions, please tell us how.
FYI - most people study for between 2 and 4 months for this test, and people who aim for 700+ scores usually need closer to 3-4 months. It sounds like you made very good progress in the 6 weeks that you studied, so that bodes well for your future study.
You ask two questions: whether you should retake the test and, if so, how to improve your score. For your first question, you should talk to an admissions consultant. They will likely want to know where you want to apply and more information about your profile (GPA, etc). You can post in a folder in our forums called Ask An Admissions Consultant.
For your second question, how to get a better score: if you took an MGMAT test, please analyze it using the below article
http://www.beatthegmat.com/mba/2011/02/ ... sts-part-1When you're done, you can post your analysis here (not just the raw data - your actual analysis of the data), and we'll help you figure out how to get better!