Hello farukqmul,
I think it's important for us to ask you a few additional questions. Do you remember what it was that held you back on the exam? Was it the time constraint, lack of scrap paper, failure to work the problems, physical anxiety during the exam, lack of strategies to effectively get through the exam, etc...
I've posted this quite frequently but I've realized that the GMAT and the Admissions process itself tests our ability to prepare, adapt, and perform. After all, aren't we expected to become the world's business leaders of tomorrow? Anyone lacking these skills will have a hard time moving forward (not saying that if you do well on the exam you possess these skills). Someone suggested taking a diagnostic. That is a good place to start as it'll breakdown your proficiency in certain areas. From there, if you can identify patterns create a plan that focuses on those weaknesses. If it's an overall problem or a lack of knowledge on the subjects being tested, pick up the appropriate books and move forward. There are just too many helpful posts on this forum to paraphrase in this thread; I'd highly encourage for you to participate in threads or at least read the ones pertaining to your situation.
Finally, a sub-500 score on one test will not necessarily dictate what you will get on the next exam. I would consider picking up all 8 Strategy Guides and absorb it. I believe this is the single best thing you can do for yourself along with a couple CAT practice exams afterward. I hope that you reflect on what it was that you failed in (most of the time, it isn't as simple as "I failed the exam") and put it out to us. Only then can we reassess the overall situation, have a further understanding of what's going on, and recommend the best plan moving forward.