i am depressed and my dad is the one remotely affected

feeling like i am nothing and that my life has no purpose and i have no future. i am depressed and i don't get why. nothing happened to remotely cause it. i am doing fine in school and i have friends, but im just sad. i am worried that if i go to a doctor and tell him about my depression, he will think i have schizophrenia or something (i don't know why i worry about this but it makes me afraid to tell him) and i am not sure if i am depressed enough to go. i am not like suicidal or anything, i am just sad. like the world sucks and i don't understand why i am here and why life is so hard. i am 17 so i am waiting for a doctor i can trust, i don't trust my dad's primary. i would schedule an appointment with him but he isn't my doctor. i just feel like no one remotely cares about me. my dad is the one affected, when i told him a few weeks ago he now tries to have "real" conversations with me and he's trying to make me feel better, but i feel weird and i don't like it.