Hi Wafas,
Business Schools generally do not care if you take the GMAT more than once - and AndrewN brings up a good point: you can 'explain away' that 2nd Score in any number of ways, so having that Score isn't something that you should worry about (especially if you earn a notably higher Score on your 3rd attempt). That all having been said, if 'your way' of studying left you open to having that type of reaction to the GMAT on your 2nd attempt, then you might need to make some significant changes to your studies (and Test-taking routine) so that you don't have that type of reaction again.
Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) When did you take your prior Official GMATs and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
2) How long have you studied in total? How many hours do you typically study each week?
3) What study materials have you used so far?
4) On what dates (or approximate dates) did you take EACH of your CATs/mocks and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
Goals:
4) What is your overall goal score?
5) When are you planning to take your 3rd GMAT?
6) When are you planning to apply to Business School what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich