Can’t go on any longer.

Hi
The reason im posting this is because i want to get this off my chest.
I’m 15 and have being suicidal for nearly 2 years now. Before the last few months i was’nt serious about suicide but now i am and need to do this.
I’ve lost alot of friends over the last following months basically pushed them away. 11 months ago a girl local commited suicide,it did’nt no her that well but she had tons of friends, she was good looking, i guess she was just depressed like me.I don’t have uch friends, i have a couple who are friends but not close, My closest was katie but was really silly and stopped talking to her over my sadness which is ridiculous then i tried to make it up with her but she said no which is probabley for the best. Another one of my good friends i pushed away too and did the same to other friends too. I am low in confidence and blush alot in social situations.
It hard when mum talks about the future on about exams in 8 weeks but don’t think i’ll be alive then.I love my mum but would’nt tell her personal stuff,
Mum and dad take things very serious, minor things and don’t think they have a clue i wanna die. I don’t want to hurt my family but i will if i kill my self but i do think to myself at least im not an only child they still have my brother.
I think about going out to the shed when mum and dad go visiting dads aunt, writing a suicide note.. thinking what to write it feels i have the note already writ in my head, i think about my mum going into the shed to find me hanged and read the note. Mum thinks i don’t respect or love her but i do so much but i think i can’t hold on much longer and i’m just going to let my family suffer. Mum lost her parents as a teenager from cancer and has gone through alot in her life. and have gone on living this long because of her and katie but not katie so much anymore, i also worry that mum will get cancer as her parents did and another local girl died 3 yeras ago and the mum died of cancer a couple of months back and i’d saw it was of stress.
I don’t no want to do i feel like my heart is tearing away and have’nt cried really yet but can feel myself breaking but still can’t cry. Im so sad and as weird as this might sound i smile when i think of being dead and hate thinking of memories of which i had with friends but no longer have many.
Thankyou for reading i had to let this out.