I just Beat The GMAT!

I just took the GMAT and got a shocking 610. My first practice test (MGMAT) that I took was a 630 (before studying at all).

I normally don't do so great on standardized exams, but this wasn't just "not doing well." After two months of studying, I would have expected so much more. The average of my GMATPrep exams was about 660, so I was hoping for a 650.

I feel like I would have gotten the same score had I not studied.
Should I even bother retaking it? What if the same thing happens? Some people are just terrible at taking standardized computer-adaptive tests.

What do you think happened? Maybe I did well on the experimental questions and proportionately bad on the real questions? Could it have just been bad luck?

Could be a variety of factors including the getting most experimental questions correct theory that you have proposed but since you are targeting a reasonable score of 650, I think you MUST retake the GMAT. Start working on your weakenesses and you should be good to go in a month