Where do you live? there are confidential advice services that might be able to help, and there is nothing stopping you from going to see the doctor and talking to him about you depression, if you doctor feels that a course of anti-depressants is the best action, then he will write to your parents and explain his reccomendation, your mother might think you're being silly of over-dramatic, but she will more than likely take heed of a doctor's reccomendation.