possible depression

for the past 5 years ive been sad deep down inside and self harming. lately, since my mom has been trying to make me feel bad, its gotten much worse. i tried to talk to her about seeing a therapist. she yelled at me. she said if i went to therapy i wouldn't be able to get a job. im 15, so going by myself isnt an option. everything seems to be getting worse too. almost everyday i think of killing myself. she knows this. she doesn't care. i want to kill myself, but it would make my best friend sad. thats one of the only reasons im still alive. please help me. i dont know what to do anymore.