Cody Graham, 20, said he was prescribed medication at a young age for depression brought on by family problems.
He said after a while he stopped taking them as instructed.
"It didn't seem to be helping me, so I just started throwing them into me," he told UTV Live Tonight.
"I started getting addicted and started getting them off the market, illegally."
He said he could get prescription tablets including diazepam, a powerful sedative, and anti-psychotic drugs from friends for pennies.
"You could get them at the click of your fingers," he said.
"It was escape from reality basically."
Cody said the tablets made him feel better when he started taking them but he quickly spiralled into a 'dark hole' of depression leaving him suicidal.
"I started getting paranoid, I couldn't sit with all my friends. I've still got some (paranoia) now."
I've tried to kill myself three times because of drugs.
He said he has missed out on his childhood because of his years of drug abuse.
He said he was able to turn his life around with the help of family, friends and FASA, a group that helps those going through substance misuse.
He says that he has now beaten his addiction and feels "on top of the world", especially as he is helping others.
"Now I'm trying to help people, younger people not go down the same road I went," he said.
Cody is now studying for his GCSEs and hopes to become a youth worker.
Over the last four years, police have carried out more than 1,000 drugs seizures.
Almost 400,000 diazepam tablets and over 10,000 temazepam tablets were recovered.
Detective Chief Inspector Todd Clements said most tablets coming into Northern Ireland are supplied through the internet, of which he says one out of two on average are fakes.
He believes that loyalist paramilitaries and dissident republicans may both be involved in the black market trade.
Belfast pharmacist Terry Maguire said that as GPs are clamping down on how much and how often they prescribe drugs to patients, the criminal market is profiting.
"There has been a policy over the last number of years, to ensure that general practitioners look at the medicines they are prescribing and there has been a major change in the way that they are prescribing and also in the numbers they are prescribing," he said.
"So patients who get medicines of this nature tend to get much less, and that's right and proper because it's important that we use them for proper clinical reasons rather for any supporting (of) abuse.
"Unfortunately, people then decide that they'll then use other sources for these medicines, which is exceptionally dangerous."
But he warned that anyone thinking they were 'legal' did not understand the law.
"They very much are non legal in the sense that they are not actually registered as medicines within the United Kingdom, and therefore they are not regulated.
"So individuals using these medicines won't really know what's in them, because they won't know the source they've come from which is what the whole purpose of pharmacy is."