Why bother?

I get dressed up for you, to make you smile, but I was obviously mistaken. You don't seem too concerned or even seem to care. I guess I don't matter anymore. Should have known you would go back with her. What have I done to lose you like this? Right now I am so stressed and angry that I want to get mad and scream. I want to hate you but it is hard. Why me? What have I done?