Hi ak1802,
First off, you've made a nice improvement to your score. A 650/Q48 is a strong performance (it's right around the 80th percentile overall) and it's considerably better than your prior score.
When a big score drop (like the one you've described) occurs on Test Day, the likely cause is due to at least one of the following:
1) Something during your practice was unrealistic.
2) Something on Test Day was a "surprise" and effected your performance.
Since you've taken the GMAT before, it's not likely that you were surprised by anything on Test Day, so I'll focus on the first possibility. I'm hoping that you can answer a few questions about how you took your CATs:
1) Did you take the ENTIRE CAT every time (including the Essay and IR sections)?
2) Since you've studied before, did you take any of these CATs before?
3) When you took these CATs, did you recognize any questions (from this Forum or some other source)?
4) What time of day did you take your CATs and what time of day was your GMAT?
5) Did you do anything that would be considered "unrealistic" when you took your CATs (pausing the Test, taking it at home, listening to music, etc.)?
6) What "brand" of CATs were they?
7) What did you do in the 3 days prior to your GMAT?
8) How did you sleep the night before your GMAT?
9) How long was the ride to the Testing Center from your home?
GMAT assassins aren't born, they're made,
Rich