As a child, he rarely raised his hand in class even when he knew the answers. He deliberately chose sport as a university course because he knew he wouldn't have to do much talking.
Years of speech therapy and elocution lessons did little to help his stammer, he says.
He gave up all hope of fulfilling a dream to become a teacher.
However, Adam, 24, from Mount Florida, says his life has been transformed by a US-born technique which he says has given him a voice.
The McGuire Programme helps sufferers control stammering through controlled breathing.
The technique also addresses the negative emotions and other psychological blocks that form in a stammerer's mind and is taught by people who suffer from the speech problem themselves.
The intensive four-day programme gave him the confidence to retrain as a primary teacher in Glasgow.
Later this year he will give a speech at his twin brother Ewen's wedding. Both would have seemed impossible feats five or six years ago.
Adam now teaches the technique to other people with the speech problem including Scotland rugby captain and former Glasgow Warriers player Kelly Brown.
He says: "If I met someone and I knew I was never going to see them again I used to say my name was John because it was easier to say than Adam.
"I struggled through school and even choose my university course based on the fact that I couldn't do jobs that involved speaking, even though my dream job was to be a teacher."
Adam's parents first became aware of the problem when he was about four.
He says: "I would find it really hard to ask to go to the toilet. My parents thought I was maybe embarrassed. It grew from there.
"When I started school, asking anything was very difficult for me. I knew the answers but didn't say it. If I did speak, it was always a struggle."
However, unlike other people with the condition, Adam says he didn't suffer any bullying in school.
It was when he went to high school that his stammer had the biggest impact, crippling his confidence. He says: "When I went to parties, we had a system where my friend would give his name then mine.
"Imagine how embarrassing that was a teenager. I tried the NHS speech therapy. When I was in the room it was fine but after I left it was the same. I also saw an elocutionist who had me reading poems. I left school in fifth year because I got good grades and I chose to study sport because I thought it wouldn't involve much speaking.
"It got a job in a gym which was fine but teaching was what I wanted to do."
By chance, Adam read an interview with former Pop Idol finalist Gareth Gates, who had been helped by the McGuire Programme. He had nothing to lose, he thought.
The programme, devised by David McGuire, focuses on costal or diaphragmatic breathing, where air enters the lungs and the stomach expands during this type of breathing.
Graeme Duffin, lead guitarist of the band Wet Wet Wet also joined the programme with great success.
Adam spends ten minutes every morning practising controlled breathing, and uses the method if he is struggling to speak during during lessons at Shawlands Primary.
He says: "It's like a sport. You wouldn't start without stretching first. My stammer can get worse if a lesson isn't going to plan or I think, how am I going to get this over to the children.
"If that happens, I just take some time to breathe properly.
"I'm really honest with the children. I say to them that if somebody has a problem with their leg, they won't walk the same as everyone else and it's the same for me with my voice.
"I'm teaching P3 at the moment and they don't bat an eyelid whereas older children in P6, they were fascinated and asked lots of questions."
Around 1% of the population suffer from a stutter and more boys suffer from the condition than girls. The term stammer is more commonly used in the US. Rugby star Kelly Brown credits the programme for allowing him to become Scotland captain and deal with live TV interviews.
Adam says he would encourage anyone struggling with a stammer to try the programme if they have had no success with speech therapy, no matter what age.
He says: "There is a man that went to the Glasgow support group that is 68.
"I remember what he said vividly: 'People might wonder why I'm bothering at this age, now I'm retired but I've had enough of my life ruled by not being able to say what I want but now, I'm not going to have that problem'.
"He's in poor health now but he had a number of years in total control of what he wanted to say."