I don't recall specifically how I did on the pre-assessment test, but it was much worse than that. In spite of many years of project management experience I was not familiar with PMI's particular PMP language. After studying for a few weeks I started taking the practice exams, which were tremendously helpful. After the 3rd exam I was testing at about 85% and was forced by circumstances to have to conclude my PMP efforts (I had another commitment suddenly looming that would preclude continuing to study) , so I just jumped in and took the exam. And passed!
So, I think Ahmed's advice is on target. Plan out your time (when I was pressed for time, I targeted 1 topic in the Rita book per day). Then take the tests and spend time digging into the questions you got wrong as well as the ones where you felt you "guessed."
You can do this, it will just take a bit of focus and time management.
Good luck!!