Is it stupid that I'm depressed? what can help me?

I've been feeling depressed lately, and not so long ago I tried to kill myself. It failed, I didn't take enough pills, and I only told two people, my best friend and my boyfriend. Who after our break up told me to go kill myself. I just find no interest in school, I find it hard to talk to my parents about anything, we're not close. I feel like my mother expects so much more from me than other mothers do because I'm an only child and my parents are divorced. My grandmother is 82 and I love her more than anything in the whole world, but she lives in America and my mother and her family don't get along, so I only get to see her usually once a year. I miss her and my family there so much. And I'm petrified of loosing her. And even though I have friends here, I just feel so lonely, and I feel like my problems are so insignificant that I'm afraid that if I tell someone no one will care. I'm 15 and I was wondering if anyone know a good therapist or shrink that I could talk to, in London, or if anyone could just give me some advise.