Hi uconn2019,
First off, a 650 is a solid score (it's right around the 80th percentile), and it might be enough to get you into Business School. You have to remember that Business Schools look at your OVERALL application and no score (not even an 800) would guarantee you anything.
All of that having been said, your 650 is also 'in range' of your practice scores. GMAC has publicly stated that your Official Score is within +-30 points of actual ability. Assuming the same potential 'swing' in your practice scores, the 650 is in your range (albeit at the low end).
I'd like to know a bit more about the practice CATS/Tests that you took:
1) Did you take the entire CAT each time (including the Essay and IR sections)?
2) When was your last CAT before Test Day (not a Club Test)?
3) What time of day did you take your CATs and what time of day was your Official GMAT?
A Q42 means that you did pretty well on the straight-forward "math" questions, but you missed out on a bunch of 'strategy' points (including a number of DS questions) and you would have made some silly/little mistakes on a few questions throughout the section.
GMAT assassins aren't born, they're made,
Rich