Is it possible for my GRE score to be wrong?

[chemnerd2]

I just got my Chemistry subject test GRE score and it's completely different from what I expected.  After studying my butt off, I took the official practice test from ETS and got ~70 percentile. But my score for the real test is 44 percentile which I have a hard time believing. I tutor chemistry for a living; I understand chemistry!! Am I in denial or could they have screwed up my score? I have a high GPA and general GRE score but I'm afraid I won't get accepted anywhere because of this and It's too late to retake the test.