GMAT Strategy

I said goodbye to my job three months back and have since been in a serious relationship with GMAT. As part of the preparation, I only completed the Manhattan GMAT Guides (total 9) and the Manhattan Official guide for review, 13th Edition. I also attempted three CAT exams on Manhattan GMAT and below is the score I achieved: 
1st - 550 - q36 v30 
2nd - 580 - q37 v33
3rd - 590 - q37 v34 
And, the real GMAT that I appeared for yesterday: 
GMAT - 500 - q29 v30 
I have always been pretty lousy at number crunching and a little above average at English, but I never expected a "500" on the screen upon completion of GMAT. With a 600+ figure as a realistic expectation, these three digits have torn me apart (just a little exaggeration, a little). Since the attack, I've been wondering about what went wrong and have been trying to tell myself that it was the lack of sleep, that is it! But, somehow, I'm finding it difficult to believe that. I slept 3 hours the night before the GMAT, and as soon as the exam started, I knew my mind is half here half somewhere far away. The score has actually shaken the future plan that was working out pretty well till now. I intend to reappear next month, and that is solely because I am not allowed to appear earlier because of the 31-day break law. In verbal, the only problem is RC, and that too I'm pretty smooth with mostly. In Quant, I literally tremble. 
Any experience out there who could just put forward a month's study plan and help a poor kid out. 
Looking forward to the magic recipe.

I took the pratice tests without AWA/IR and on the couch. And an icing on the cake, slept 3 hours the night before. The tests were strictly timed though, with 8 minutes optional breaks. Could you please suggest how to strengthen the quant area in about a month's time. I was thinking of skipping the probability all together and focus on things I know I won't get tangled in during the real thing. Is this a right approach?

Thanks for your feedback Ceilidh.