It sounds like you got a tough break if you were consistently in the 600s during prep. Did the testing conditions get to you?
I would definitely recommend a retake since your GMATPrep were significantly higher. I think you have to wait 30 days before you re-write it so keep studying. If you're not already using the MGMAT guides
I would highly recommend them. Also, if you're not already simulating a full test experience (AWA, 8-minute breaks and all) then you should do that as well.
Don't give up hope. Everyone faces a few bumps along the way. Persistence will eventually pay off. Wish you the best!