"I missed out on getting to know my mum properly," Peter says.
"It would be great to hang out with her as she was but it's not going to happen so I can't sit on that thought for too long."
The 19-year-old is in his garden as his mum is looked after by two carers in the house. Doctors expected her to die three years ago.
She has Huntington's disease, a rare genetic condition that affects the nervous system.
Peter isn't his real name, we've changed it for legal reasons to protect his mum's identity.
"There's a 50/50 chance I have it but I can't worry about that now," Peter tells Newsbeat.
"I can get tested and I did intend to, however at this point I'm 19 and I don't need to know now.
"It's a problem for when I'm 40. I don't have time to worry about it."
There is no cure for Huntington's disease and Peter knows he may develop it later in life.
"She can't do anything. She can't swallow. She can't have any solid foods," he says.
"The next stage is death but that could be anytime.
"We're basically waiting on pneumonia or a heart attack. It could be two weeks or it could be two years."
Peter recently went to the Court of Protection, external. It decides things for people who don't have the mental capacity to make decisions.
He went to get control over his mother's finances and to make sure she stays at home "until the end".
Peter won his case.
"I make sure she has the money for her trips out.
"It's not too difficult in itself, it's just more that I've been trusted with it. I just have to make sure the bills are paid."
The judge who ruled on Peter's appeal said he was "mature beyond his years".
He thinks his mum knows he's in charge of her finances but says she probably doesn't understand what that means.
Peter says he gets frustrated all the time but buries it.
"A lot of the time you are quite helpless because you can make a life as comfortable as possible but you can't change what's going to happen and what is happening.
"There's nothing I can do to make her able to walk again.
"Emotionally it's incredibly draining. It makes me quite a cold person a lot of the time. I can't deal with a lot of it so I shut it out.
"If you think about it everyday it will drag you down."
Peter has just finished college but will wait to go to university.
"I could go to university but I think with mum's time span it would be bad to be doing university during her last days," he explains.
"I'm going to defer that until things are a bit calmer."
He says he used to find it odd when his friends would need to ask their parents permission to do something.
He never had to do that.
"The relationship I built up with her was not one of a mother and son. There was a point in which our mental ages crossed over.
"It developed as a little sister kind of relationship.
"I think of her as a sister that I need to protect."
A lot of his friends don't know the extent of his mum's illness.
"I find the main thing is they never know how to react," he says.
"It's more that I don't want to make them uncomfortable.
"For me, this is my normality. I don't know any different so I don't long for anything different."
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