Can you please help? Im hurting badly.?

Okay, I'm 13 and my mom and dad lately have been total b*tches to me! Sorry for my language but I'm just so angry!!!!!!! Anyway, i have lived with my great grandmother since I was 2. But my parents always try to control me. If you ask me, they aren't real parents because they don't take me to the doctor, they don't buy me clothes, they don't buy me medicine, they don't put food in front of me, they don't do anything a parent should do. My grandmother does all of this. The only time they do something is to go yell at my teachers for gettting a B or C!!!! Me and my grandmother have been talking about taking legal action for a while but she doesn't wanna "hurt" my so-called dad. He always blames me, makes fun of me, pushes me, oh and did i mention he blames me?!?!? For everything!!!!! I have been really depressed the last couple of years, and I don't think a 11-13 year old should be depressed, i cry myself to sleep most nights because of them. When I tell my grandmother we need to take them to court she says, i don't wanna hurt your dad! She is able to take care of me because her and my uncle own a buisness that gets about maybe $300,000 a year. They split it. So there are no financial problems. But how can i convince her that she needs to take legal action against them?