My circumstance differs a bit but I am just as concerned as you are. On all my practice before the real LSAT I was scoring pretty low and I know I needed more prep so I registered and planned to sit out of this October LSAT. However I noticed the days I took those few practice exams I was on adderrall because I was prepping all day in the book store before from 8 to 6 then class from 6:30 to 10. So I took the online exam the next morning (while not on adderrall) and jumped up from low 140s to mid 150s. I feel as though those things were holding me back, so I locked in and went in there for this exam. It was the first didn't I rarely guessed (maybe just two questions) and I dont feel overall too bad about it. However, the realistic part of it is that your practice scores are good indicators? So I dont know what to think, but I haven't canceled yet because I felt pretty good about the exam. I think you'll be just fine as I hope I will as well.