My dad just died and I feel so alone?

My father passed away a week ago due to a sudden illness caused by his lung cancer. So everyone knew he was ill, but the death was still very quick and unexpected, as he had been responding really positively to chemo and radiotherapy. He was the centre of my world, and I adored him. I have a very difficult relationship with my mother and stepfather and he was always there for me, never belittled or patronised me, always listened. I feel so alone and lost without him, like I now have no one left in the world who truly cares about me. As well as this, my boyfriend dumped me yesterday because he doesn't want to have to deal with my grief and the pain of my bereavement. I feel so absolutely abandoned. I don't feel I have anyone to turn to, because my dad was always the one I went to when I was scared or upset or confused. I'm only 18. I don't want to have to face the rest of my life without him. I want someone to come and take care of me and be there for me like my sister's boyfriend is there for her. I don't have anyone, and it's worst at night with no one to talk to, no one to call or text. I miss him so much. I don't know what to do. Everything makes me want to cry. I just want to fall to sleep and never wake up.