if you're constantly arguing about trivial, insignificant things then someone has some deeper issues that they're not being open and honest about. your line stating "it still seems somtimes that no matter what I do, we alwys end up in a fight." leads me to believe that it would be her with the issues.
the first step is to find out what these are and the best way to do that? ask her, of course. however, you need to approach her in a very nonthreatening, nonjudgemental way and reassure her that you only want to understand where she's coming from and what she's feeling. do not get defensive if she says something that seems like an attack... just calmly ask her to clarify or give an example or two.
there's a chance that she may not even be completely aware of what the problems are, but she likely has a general idea... so let her think outloud to you and mimic what she says so she can hear it herself. once you figure out what's bothering her... share what's bothering you. after everything is out in the open, work together to find some answers and solutions. if you both truly listened to each other, this step should be fairly easy. good luck.
