what to do

Some things that anger me in my relationship are that my girlfriend acts like she knows everything. She tells me that she just has this feeling that I am up to something or hiding something and I am not. I think that she is just so afraid of being hurt that she is afraid to trust me. I have also noticed that she can not stand to feel like she is in the wrong. There are times that she will ask me a question and I will answer her and she thinks I am snapping at her. I feel like no matter how I answer her or no matter what I do it is not good enough. I love her but I don’t know what to do.