"He just wanted to protect me. I wish I had known because I could have done so much more," his devastated mum Jaime Green told Gloucestershire Live.
"He suffered in silence, he didn't want anyone to know."
Jaime wishes she had known the seriousness of his condition, but she his final moments were an unselfish act and one that captures the type of man he was.
"To not say anything about what was happening to him ...
"He was just a hero.
"He didn't want to be wrapped in cotton wool. If I tried to talk to him about certain things, he would say 'Don't be so deep mum'," Jaime said.
"He was always about everyone else."
Jaime had been Ben's full-time carer at their home - saying that her son showed remarkable strength to not tell her of his darkest fear.
Jaime and her husband Phil Green are now trying to console Ben's nine siblings following his death.
An online fundraising appeal has been set up to help pay for the funeral.
"So as everyone knows Ben passed very suddenly and a lot sooner than any of us can imagine and this was a massive shock to our family. He battled cystic fibrosis like a boss. He kicked its ass for so long but on Saturday November 11 he couldn't fight no longer!! He was loved by so many and I just want to help take some of the financial strain away. l so please everyone that knew and loved Ben, please even if it's £1, it will all help", Jaime wrote on the JustGiving appeal.
Phil told the media Ben's friends are taking the loss personally, with many feeling guilty for not being in touch with him recently.
However, Ben's father says the family did not want anyone to feel regretful, and instead urged friends and family to cherish the good times.
Devastated by his death, Jaime said: "I'm struggling, it's so raw, I'm a lost soul at the moment.
"You couldn't ask for a better son. He was absolutely incredible - so loving, so caring. He could be so poorly but would worry about everyone else."
Jaime plans to have her son's coffin carried to the church in a VW campervan, saying it will be "like he will be going on holiday", something Ben would have loved very much.