depressed and bad grades

I am too depressed to do anything, I can’t get any homework done because im too depressed, I just look at dead girls on the internet and masturbate, then I suffocate myself and masturbate, then I cry and punch the walls, then I go to sleep. And at school Im too depressed to focus on my work, No one understands how I feel, I already trusted someone before and now even if people know about my depression it just makes things worse