I am awfully worried about my girlfriend, who keeps having these headaches on one side of hear had only - the left side. At the same time, she says she feels sick. Reading on the internet, I did see that some articles say that this can be a sign of a brain tumour but when I mention this to my girlfriend she just brushes it off as if it is nothing. I do wish she would just go to the doctor! But in the meantime, I'm hoping you can give me more info about these kinds of headaches? Perhaps your answers can help her!