Reece Williams fell over up to 25 times a day and sometimes slept for 23 hours - but doctors were baffled about what was causing it.
But Reece's desperate dad was so determined to find out a cause that he researched the boy's symptoms on the internet and then made videos of Reece collapsing into a slumber to show doctors.
Now, thanks to controversial drug Xyrem, which is only formally licensed to treat adults, he is at last able to play and sit in class without suddenly falling asleep.
Reece was five when he began suffering symptoms of narcolepsy and its sister condition cataplexy, a sudden weakening of the muscles.
Both can be triggered by strong emotions like excitement, laughter, surprise or anger. In Reece's case his problems got worse over time.
His mum, Chantelle Burrows, said that Reece went from a loving, happy-go-lucky boy to being moody and aggressive.
"We started putting him to bed earlier but he got worse and worse," she said.
"His teacher kept stopping me saying she was concerned. He would fall asleep in the middle of the class. It meant he was falling behind on his school work.
"We had to get a pushchair for him. He couldn't even keep his eyes open to eat. He looked exhausted all the time. He was terrified to go to sleep at night because he was having vivid nightmares. He would refuse to get into bed."
Later, they took him to A & E at Birmingham Children's Hospital, but after extensive tests, doctors couldn't find out what was wrong.
But Chantelle's partner, Luke Williams was determined to find out the cause and typed Reece's symptoms into a search engine and the rare sleep condition narcolepsy came up.
He said: "Reece had all the symptoms. I'd also started to notice that when he laughed, his face went all funny. It was like a switch and he would just fall to the ground."
It was then that Luke came up with the idea of filming Reece every time he collapsed to show to the doctors.
The footage helped medics to diagnose Reece with narcolepsy and cataplexy, a sudden weakening of the muscles triggered by strong emotions like excitement, laughter, surprise or anger.
When doctors monitored his sleep patterns, they were stunned to discover he was in a deep sleep after just 19 seconds.
It normally takes the average person about 40 minutes to fall into a deep sleep. Doctors tried to treat Reece's condition with high doses of different medication but nothing worked.
He has since been put on Xyrem, which is used to reduce daytime sleepiness in patients as well as the number of cataplexy attacks.
The drug, which he has to take three times during the night, has improved his condition and now he can have a kick around in the park with his dad.
Luke said: "It means the world to me. It's all you want for your child - to be able to go out and play.
"Reece is football mad. He supports Aston Villa. Six months ago, he wasn't even able to kick a ball.
I worked out it was the build up to kicking the ball that made him collapse. It was the excitement.
"We tried everything, even playing in silence, but it was no good. He'd get angry with himself. We used to just go home.
"Xyrem completely knocks Reece out for 12 hours so he is more awake during the day. It's an improvement but he sometimes still falls asleep. The doctors are really pleased."
Dr Paul Reading, president of the British Sleep Society, said: 'Narcolepsy probably affects one in 3,000 people and can often start in childhood.
"The main symptoms of narcolepsy are unintended and irresistible naps through the day, episodes of collapse induced by emotions such as laughter (cataplexy) and disturbed sleep at night, often with vivid nightmares. All these elements may severely affect a child's quality of life and education.
"The most effective drug for narcolepsy is Xyrem although it is only formally licensed for treating adults. It is also a controversial drug, largely due to its high cost."