I think im depressed....?

Im a 15 year old girl, biual, im struggling with my uality and relationships at the moment and Well i dont know, when im with my friedns i think im happy, i have a good time with them but when im alone i just dont do anything, i either go on the laptop or just sit around listening to music that describes how i feel at the time like for example now im listening to sway sway baby by short stack. I get miss treated at home, me and my mum live with my grandad in his house and he is a complete to me he always calls me ignorant, embarasment, *****, dirty pig etc and its really hurtfull and i always retaliate with violence back to him and that doesnt help. I have had suicidal thoughts before and i just dont really see the point in anything, my school grades are going down and all this started when i lost my best friend about a year ago for various reasons but i miss her and iv been getting more and more agresive i have spoken to the school phsycoligist but she doesnt know what shes on about. Im trying to get a referal to a proper phsyc but its taking a long time. Help anyone?