Hi dtn528,
GMAC has publicly stated that the Official Score that you earn on Test Day is within +/- 30 points of actual ability. Assuming a similar 'swing' in how your CATs function, your score results show that you essentially performed the same each time (+/- a few points). By extension, your current ability level is in the low-600s.
Based on the information that you've provided, you took your CATs in a rather inconsistent fashion. As a result, you were NOT properly training to face the Official GMAT - so you were not ready to score at a much higher level on Test Day. Test Day is a rather specific 'event' - the details are specific and they matter, so you have to train as best as you can for all of them. The more realistic you can make your CATs, the more likely the score results are to be accurate. By skipping sections, taking the CATs at home, taking them at different times of day, etc., you weren't properly training for the FULL GMAT 'experience.'
Thankfully, this is a relatively easy set of problems to fix. First and foremost though, you have to define your goal:
1) What is your overall score goal?
The answer to that question will impact how much additional work you have to do. You'll certainly need a new set of practice CATs to work with and you have to put in the necessary time to train your brain (and body) for the Test conditions that you'll face again. You might also need to invest in some new GMAT training materials.
GMAT assassins aren't born, they're made,
Rich