Hi viper1991,
I'm sorry to hear that Test Day didn't go as well as hoped. Since some of your practice CAT scores were so much higher than your Official Score, it's likely that either something about your practice was unrealistic or something about Test Day was so "off" that your performance suffered.
If you can answer a few questions, then we should be able to figure this out:
When you took your CATs:
1) Did you take the ENTIRE CAT (including the Essay and IR sections)?
2) Did you take them at home?
3) Did you take them at the same time of day as your Official GMAT?
4) Did you ever do ANYTHING during your CATs that you couldn't do on Test Day (pause the CAT, listen to music, etc.)?
5) Did you ever take a CAT more than once?
On Test Day:
1) How long was the ride to the Test Center from your home?
2) Were there any distractions at the facility or during the Test?
3) What did you do during the two 8-minute breaks?
4) Did you finish any sections early?
5) Did you have to rush to finish any sections (and guess on questions just to finish on time)?
It's possible that you just had a "bad day"; but we really need to nit-pick these details and fix whatever issues need to be fixed before you go in to retest.
GMAT assassins aren't born, they're made,
Rich