Suffering from psoriatic arthritis, a "miracle drug" stopping him becoming severely disabled is no longer working. In a week's time he starts a new drug in the hope that the decline will be arrested.
As an 18-year-old, Stephen was standing between his father Sammy Gault and Ted Armstrong when the bomb exploded.
Both his father and Mr. Armstrong were killed as a result of the blast. "I was only 18. To see my father lying there dead and the man beside me dead, it is something I will take to my grave. I remember it as if it was yesterday," he said.
"I remember hearing the explosion and going forward. For quite a few seconds, there was an eerie silence. You could have heard a pin drop. Then I heard a shop alarm ringing. I could not breathe, choking with the waste and dirt and I could not see.
"Then, all hell broke loose and there was screaming, children screaming. I could not move. My dad was lying across my feet. He had his head through the railings. I knew right away he was dead. Somebody pulled me over the railings. I was told my leather jacket saved my life. It was cut to shreds. It had saved me from the falling slates. Ted Armstrong was on the other side and was dead".
Prior to the bombing, the morning had been uneventful. He had left his Castlecoole home with his mother and father. His leather jacket, bought the day before by his father, was the subject of conversation that morning as his mother, Gladys, had not wanted him to wear it. His mother went to St. Macartin's Cathedral to act as an usher while he and his father made their way from the car parked at the library to the Cenotaph. His father knew a lot of people and there was plenty of friendly "chit chat". Spotting his wife's cousin, his father had called him over. "Thankfully, he didn't come," Stephen said.
The emotional scars have run deep. While his injuries on that day were "superficial", his health since then has been profoundly affected.
"Two weeks after the bomb I developed psoriasis. 95 per cent of my body is covered in it. I have psoriatic arthritis. I had surgery in 1999 to correct my right hand. When I was 29, the surgeon said I could be in a wheelchair by the time I was 40. In 2006, my condition rapidly got very, very bad. I could not get out of bed, could not drive, I could not wear shoes, could not lift a knife or fork. Thankfully through Arlene [Foster] and Sean Coll I got a miracle drug, an injection twice a week into my stomach. At the start it worked. Unfortunately the drug now does not do anything for me. Hopefully I will start a new treatment in time at Altnagelvin, It is a chemotherapy drug. This is the last chance," he said.
"When I think back and being told I would be in a wheelchair, to someone I would regard as being still young, it is an awful thing."
Commentators have said over the years that Martin McGuinness was the IRA Commander involved in approving the bombing but he has always denied it.
"I was in Stormont in the middle of victims and the Deputy First Minister walked through them. How ignorant can someone be?" Stephen asked.
"We cannot go on the way we are going. Victims have to be remembered. Twelve innocent people were murdered in the streets of Enniskillen 25 years ago.
"I personally think Enniskillen people have never got justice. I do not think we will ever get our justice," he added.
There has been "delay after delay" with the Historial Enquiries Team (HET) report into the Enniskillen bombing. "My impression is that they have something to hide. is it because of who is in Government? I do not know. I do not think Enniskillen will get closure. As for closing the door, Enniskillen will always be an open case in my eyes," he said.