I'm sorry you had a rough test experience.
It will be useful to know the exact Q and V scores both from your real test and from your practice tests. Also, did you take your practice tests under 100% official conditions, including essay, IR, length of breaks, etc.?
There are a number of reasons why your real score might have been lower than practice scores. Your practice scores might have been artificially inflated (by, for example, skipping the essay or IR sections, giving yourself longer breaks than allowed on the real test, etc.). You might have messed up the timing; this can cause significant score fluctuations. You might have experienced strong anxiety on test day. (We all feel at least a little bit anxious, but for some, the anxiety is strong enough to affect test performance.)
You'll need to try to figure out what happened - starting with the data I asked for above.
Also, use the below to analyze your most recent MGMAT CAT(s) and compare to how you did things / how things went on your real test (to the best of your memory):
http://www.manhattangmat.com/blog/index ... ice-tests/Then come back here and tell us the results of your analysis and what you think you should do based on that analysis. We'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw data. Part of getting better is developing your ability to analyze your results - figure out what they mean and what you think you should do about them!)
I did not used any other guide except the OG and the GMATprep software.
This is not enough for most people. Test questions are good practice, but the questions themselves don't actually teach you how to get better at answering the questions, and most people can't lift themselves to the highest scoring levels simply by doing lots of questions. You will need some resources that will break down the question types and content for you and help you get better.
Read this:
http://www.manhattangmat.com/blog/index ... -the-gmat/There are a lot of additional resources linked in that article. Work your way through them. Pay particular attention to the sections on time management and how to study.
And read this, which talks about the kinds of resources people need to study (beyond OG and GMATPrep):
http://www.manhattangmat.com/blog/index ... an-part-1/