He said he was 'kind of stuffed' - adding 'you can't win them all'. He fulfilled his dying wish to attend his school leavers' prom on June 28 and outlived everyone's expectations by six weeks.
He fell into a coma on Sunday and died at his home yesterday.
His mother Sacha tweeted: "6.10am 14.8.12 DD died by love at home."
Days before his death David told his mum and dad Toby he had 'very much enjoyed myself here' and asked for his ashes to be scattered in a stream where he used to swim.
Sacha also revealed how she had found her son's will, leaving his possessions equally between his younger brother and sister.
She tweeted: "Found DD's will: sharing his things btween bro & sis (jellybeans 2 little sis, of course); ukelele 2 fam. friend. So organised."
In order to raise awareness of brain tumours in children, Sacha has been using Twitter to promote the charity Headsmart and update her followers on David.
Sacha, 44, a singing teacher, continued to mark her family's journey on the micro-blogging site and David's incredible outlook on life.
He spent his final days swimming in the stream at the bottom of the family's garden, cooking, and doing jigsaw puzzles, but desperately wanted to go to college and study biology.
David, from Fontmell Magna in Dorset, had undergone several operations since the age of 11 to remove the golf ball-sized Medulloblastoma tumour but suffered two relapses.
Children have the same risk of developing a brain tumour as meningitis, and Sacha is now campaigning to make other parents more aware.
She hopes to get small cards made by Headsmart, a charity promoting brain tumour awareness, in every school across the country, listing symptoms to look out for.