Did you try Covey in the middle of the semester? Did you start using GTD right around midterms? One of the problems with moving into any of these systems is that once you've got everything organized you still have a ton of stuff to do. If you started out way behind schedule, creating a system of personal management isn't going to change that. The problem is that getting on schedule usually requires actually getting ahead of schedule -- start early on every project and you'll finish early on every project. But if you can't start on your brand new project because you're still finishing that last project, it becomes very hard to catch up. You need some span of time in which nothing new comes to you so you can wrap up all of your loose ends. You may have to wait until the end of the semester before you really catch up, but then you can start the next semester with a working system in place and hopefully avoid the same problems.

Which is the important part. Now that you have a system in place, get used to it. Develop those better habits, don't let yourself backslide, but remember that getting organized is a process and that it doesn't usually happen overnight. I've been using GTD for a few years now, and I'm still altering my system and habits once in a while. Be patient, keep at it and really examine what is and isn't working (and most importantly why). Eventually you'll notice improvement and sooner or later you'll wonder how you ever got anything done before. You just have to really hammer away for a while to catch up on all the stuff you fell behind on.