Very poor 570 because of stress! Need retake strategy...

Hi there

I took the GMAT today and got a very poor score pretty much only because of the effects stress had on me.
570 Q36/V31

I have been preparing for the GMAT for about 8 months (although have been focused on prep for 4 months really). I started off with a 520 and slowly reached the 680-700 level. Some of my last scores were 660 (Q44/V38), 680 (Q44/V39), 690 (Q44/V40) and 710 (Q43/V44) on GMAT Prep. My initial goal was 710.

I know I can do at least 680, but my stress level reached a peak during the week before the GMAT because the D-Day was getting closer and I got a 660 and 640 in the two previous tests, which made me wonder about my abilities. My stress was so high that it made me literaly sick during the weekend, I didn't manage to eat properly during these two days before the test and was feeling pretty weak physically, and that made me worry even more... Last night (because of stress again) I didn't fall asleep until 3am, which left me with only 3 hours to sleep before the test!!
Well, no need to say that my brain was unable to think this morning!

Anyway, I've learned my lessons: work on stress levels and ensure that stress doesn't affect my health, and book a test date for later than 8.30 in the morning, I realized that this is a bit too earlier for me.

But now I have to do the test again and I want to put in enough work to ensure a 680 minimum score. So far I have been working mostly with Manhattan GMAT books and CAT tests and did both GMAT prep tests a few times.

I still have to build a retake plan but here are a few things I thought about doing:
- work with GMAT Club tests (used only the free ones but thought they were very helpful)
- use GMAT club forum more to understand how to solve problems
- re-examin my method to attack a problem (with a tutor/friend)
- fix my quant weaknesses (with a tutor/friend)

Do you have any other ideas/suggestions for a retake plan?

Also, I have used both GMAT prep tests quite a lot already and am not sure whether it will be really indicative of my score if I use them again. Any opinion on this?

Thanks!!!