When taking the practice exams, did you make sure to time yourself properly and put yourself in a quiet, test like setting? Often times, I think people give themselves more time than they should or realize and it skews the scores higher since obviously, more time you have, the better most people's scores would be. Also, I took all 3 practice exams, they were fairly close for me, however, if you only took one, then maybe that test just wasn't the best indicator.
I know it's a lot of money to spend to buy all three, but for me, it was worth not having to deal with re-taking anxiety/cost and such so I went ahead and purchased all available. I definitely wouldn't take just one exam and think that that one exam is going to predict my score exactly.
I also went through my practice exams a few times after getting it scored. It helped tremendously with speed that by the end, I could set up and solve ALL the problems with time left to spare. Personally, I think the PCAT is more of a time crunch tester than anything. Wish you guys the best of luck