Need Help Horrible score in gmat!!!!

Hello everyone!!!
I gave my gmat on August 25th 2013 after at least 8 months of prepartion. I am very sad to say that i just managed to score 540 (Q-40,V 24).
I really dont know what went wrong.
For my prepartion i did OG 13,OG 12, OG11, OG 10
Quant 1st edition
Quant 2nd edidtion
Verbal review 2nd edition
Initially i was weak in CR, RC and quant. even though im not a native speaker i managed SC. my accuracy rate in all og's was 85% for sc.
After doing dese many og's and verbal review i was doing good in CR but RC was still a problem for me.
I did all the cr and rc questions from Gmat prep.
For my quant did all the books mentioned above.my test scores were

gmat prep1 :700(q-50, v34)
gmat prep2 710(q-46,v41)
Manahttan all tests average score :650 (Q-range 41-44, verbal 35-37

i even left my job for full time preparation. I was really confident that i would get above 650 at least. i dont know wat happened. on the exam day i got really confused with first few questions in quant, i was not sure about their answers and wasted a lot of time on these questions, Similarly in verbal first few questions were really confusing nd again my timing got in screwed in this section.
im really confused now dont know wat to do. I just rebooked my date for 21st oct,2013. But i dnt know from where to start i put so much effort the first time but still ended up with 540
I have joined gmat club tests to improve my quant score. But i still feel my basic concepts are not clear.
Any advice would be greatly appreciated