Hi trangle1611,
From what you describe about being denied entry to the Exam and scrambling to get your passport to the Test Facility - you likely experienced far more stress than you ever would have during your practice Exams - and THAT almost certainly impacted your performance. In addition, taking the GMAT in a 'new' order was probably not a good idea (since you had not trained for that order).
Test Day is a rather specific 'event' - the details are specific and they matter, so you have to train as best as you can for all of them. The more realistic you can make your CATs, the more likely the score results are to be accurate. The more you deviate, the more "inflated" your practice scores can become. Now that you've experienced the Official GMAT, you have to make sure that you take your CATs in a realistic fashion that matches up with what you'll face on Test Day (so take the FULL CAT - with the Essay and IR sections in the same order, take it away from your home, at the same time of day as when you think you'll take the Official GMAT, etc.).
Since there was so much anxiety on Test Day, it's likely that this score result was not your best work - and that you could score higher under better circumstances. As such, you could potentially continue to study as is and hit your score goal. Considering your lack of a formal study plan the first time, and the potential to pick up points in BOTH the Quant and Verbal sections, you might want to consider investing in a GMAT Course for this next attempt (either Guided Self-Study or instructor-led).
GMAT assassins aren't born, they're made,
Rich