Why do i feel this way i feel so sad and alone and dont want to carry on?

for about 2 years iv hated my life im 19 and i dont think i have ever realy been happy i realy dont want to be here but we lost my brother on valentines day this year he killed him self everyone says it was selfish and wrong i no it was but i can understand how he feels.I feel like iv got nothing to live for no1 to talk to.If my brother didn't go i wouldn't be here now i cant pout my mum and dad throe that pain again i just feeling so low and having to pretend ever things ok when im with any.I dont no what to do.