Hello
Sorry for the late response.
Please do not feel sad. Everything will be just fine.
No matter what your age is, you can ask for help.
It might be the anxiety that holds you from telling your mom about your feelings. I read your post and it looks like you are a brave person. You do things that have to be done even if they look a little frightening. Your mother is there to help you. I'm sure that she wishes only good to you and it will cause no harm to tell her. Please go and tell her about your anxiety, and let her know that you want help. It is not a bad thing to ask for help. On the contrary, it is appreciated.
Your brother and sister don't need to know about it. You can ask your mother to help you find something to tell them, if it is important to you that they won't know about it.
Good luck