Johnson has admitted to grooming and kissing the girl but has pleaded not guilty to two further counts of sexual activity with a minor.
Johnson said he admitted to police he had kissed the girl in his car but said he tried to "play it down" due to the severity of the accusations against him.
"My world had got turned upside down and I was trying to play it down as much as I could," Johnson said.
"I was panicking.
"I had all these thoughts going through my mind about everything.
"To name a couple: my career, my family. I was in turmoil."