A real test is adaptive; the OG has questions ranging from very easy to very difficult. If you are a high scorer in one area, then you'll find most of the OG questions on the easier side.
Tell us more about what happened during the test. Did you have any timing problems? Any stamina or mental fatigue issues?
What kinds of scores were you getting on your practice tests? Did you take your practice tests under 100% official conditions (including essays, length of breaks, etc.)?
Have you taken an MGMAT CAT recently? If so, use the below article to analyze your results. If not, take a CAT and then analyze your results. :)
http://www.manhattangmat.com/blog/index ... ice-tests/After, come back here and tell us your analysis. (Note: not just your raw notes - make sure you also tell us what you think the data means. The ability to self-assess is crucial to your ability to improve.)
Also tell us what study materials you have (including what you have and haven't used yet).
Finally, what's your goal score? A 690 is already a very good score! You mention "looking for 99th percentile) - do you mean you want a 760+? Why are you trying to get such a hugely high score? The only school that requires a score like that is... ManhattanGMAT. ;)