I feel you man. I took 9 CATs in a span of 6 weeks and felt great going into my last GMATPrep test before my real test. After scoring a 660 on an ARCO CAT, I scored a 580 on the final GMATPrep. It made me want to punch a baby! (just kidding, but you understand)
I ended up with a 560 on the actual. I was totally shocked and felt hopeless because the actual GMAT was easier than any practice CAT I had taken before. I even got a little giddy during the Quant section cause I thought I was doing so well. I cried in my beer for a day, then I went out and found a tutor.... story to be continued...
The one uplifting thing I can tell you is what I heard from my tutor - he had a student that never scored higher than a 590 on any CAT and ended up with a 720 on the actual. My tutor himself, who scored a 760 never got higher than a 630 on the CATs.
You just have to jump in there and take the real thing. It might work, it might not. But at least you tried and the beautiful thing is - you can take it as many times as you want... but don't take it more than 3 times 'they' say, "cause adcoms will wonder what's going on with you." :)