you should find yourself a testmasters or (my preference) a Powerscore course. If you can't do this, pick up the logic games bible and the logic reasoning bible, published by Powerscore. You can find it on their website, powerscore.com. You can also find out if there's a test prep company around you.
And you should try some meditation or something, since there's obviously some stress/pressure issues here, and if you can't beat that, then studying for hours on end won't end up helping any. Although taking prep tests should help alleviate some of that stress.