You don't have any obligation or duty to tell your mother if you don't think that it will help you to do so. I suggest that you try the counsellor at your school, next week. As HazelGirl says, a counsellor should not judge you based on what they know about other people, and most will not - although some are not as good at their jobs as others. But if nothing else, she will be able to tell you what possibilities there are for you to find help.
Keep us posted?