I was having a similar problem because I was never used to studying for long periods of time - like you need to do for the DAT. It might sound weird, but I got this Bi-aurial sounds app for my iPhone and it had these weird sounds that supposedly lets your brain focus more - it might just be the placebo effect, but I thought it let me focus better. I know you can probably find a similar mp3 online. It's just like these weird staticy waveform sounds.