Doubting the CAT Pearson system of NCLEX

I failed for the second time and money is not that easy for me... Is it possible that the Computerized Adaptive Test (CAT) of Pearson for the NCLEX is not as accurate? People who are less "smarter" than me in our class get to pass the NCLEX in their first time.. and some who are top of the class get to retake like atleast 2 times before passing... I mean on my first try i answered 102 question, failed to 2 subject and on my second take i answered 215 question and failed 3 subject,when i know more than before... A professor on NCLEX review class told me that it is really sometimes "luck" and it depends on the selected questions of the computer.. i mean isnt that unfair that some people get to answer easier set of question than others...