My wife is about 13 weeks pregnant. Why is she acting totally crazy?

I think I'm a good, reasonable husband. I am supportive and try to be empathetic to her. I really try to go over the top to take care of her. Everything I do gets a totally emotional, crazy response, and she tells me I'm mean. I feel emotionally paralyzed and terrorized by her. I'm afraid to do anything because I feel it will result in some emotional trauma. I love her, but I totally hate my life right now.