Thank you so much for writing in for help. You are wise to recognize that you need to talk with someone about your pain and reach out for help. If you have a trusted teacher at school, or a school counselor, they may able to help you find a way to talk to your mom about your struggle with depression and self-harm.
If it seems a little easier to talk to your mother about physical health concerns you may want to try asking your mom to take you to your physician by saying something like, “I haven’t been feeling well for a while. Will you take me to the doctor?” Your doctor will be able to do a depression screening, rule out any physical illness, and give you some recommendations for therapists in your area.
I would recommend individual therapy to address your depression and self-harm, and family therapy to help you and your mom communicate better.
If you can’t talk to your mom, please talk to someone soon. Depression is treatable. You don’t have to continue to suffer.
Please, take good care of yourself.