Forbidden diaries

Last week my bf got his wisdom teeth removed. Strangely, I had fun taking care of him. Im the happiest when I can help other people or make them happy. Im sad when others are sad.
However, I have to confess something. My mom writes a diary. And I found it lying on the piano two weeks ago. I didnt know what it was until then. And what she wrote didn't let me go. I know I shouldn't have read it, but I couldnt stop the moment I found out what the little notbook was and how sad she is. She complains about her boss, my dad and us kids, mostly the boys. I know its a lot, we could help her more etc. But I really thought that at the end of the day she was happy that she had us. It shocked me that I was wrong. I try to help, but then I don't live at home anymore and am not around too much. She didn't complain about me in her diary. She didnt even mention me in the last three months. Why? I'm a very quiet person, but I try to let her be part of my life. Maybe I don't worry/annoy her that much. But to me it seems she never thinks about me at all. I wish so much I/we could be a joy to her heart. But I don't know what I can do? I try my best (cooking dinner when Im home so she can relax, going shoping for her etc.), but does she even realize it? I love you so much mommy, Im so thankful for everything you did for us, I LOVE YOU forever and no matter what you say or do.