Mr Whittle, 51, a life-long Liverpool supporter from Burnley, suffered post-traumatic stress as a result of what he experienced.
He said: “There were so many people on Leppings Lane you couldn’t move really. Eventually, I found myself at the front, near gate C, where fans were packed up against each other, it was quite painful.
“That’s when the police opened the gate and people flooded in. Everyone was showing their tickets – this myth about ticketless fans, it’s just rubbish.”
Mr Whittle, who first attended a Liverpool game at the age of five when he was taken to Anfield by his grandfather, blames South Yorkshire Police’s management of the crowd for causing the disaster.
“Once the gate was opened the obvious place to go was down the tunnel into the central pens,” he said. “In the previous year, the tunnel was closed off when pens three and four, the central pens, were full but that year it wasn’t closed.
“So everybody went down the tunnel, into those pens and it became overcrowded.
“I heard a lot of shouting, people saying someone is going to get killed, someone is going to get hurt.”
Mr Whittle recently published a book, With Hope In Your Heart, about his experiences at Hillsborough.
He added: “The tunnel was dark, very dark. I almost fell and there were some people crushed underneath. I was pushed from the back into pen four and was rammed into a barrier.
“I managed to get a small gap to push back but then a bigger surge came and I went to the floor.”