Dwight Gooden, once the king of New York baseball, today sits in a Florida prison, serving his first extended jail time after violating probation by using cocaine in March. Yesterday, Gooden gave The NY Post his first interview from behind bars. The 41-year-old former superstar sat in a conference room at the Gainesville Correctional Institute and shared his experiences from prison, where he’s been since April 17. Gooden is currently in a medium-security prison, but he spent his first 10 days in the Reception and Medical Center in a one-man cell, something he describes as “torture.”

GAINESVILLE, Fla. – Dwight Gooden stared at the walls, which he swore were closing in on him. He asked himself if he was dreaming. He had to be. There could be no way it had come to this. He was in hell.

No phone calls. No TV. No sunlight. No contact with anyone other than a prison guard. This is how far he’d fallen – Doctor K in a prison cell. The guards would put him in handcuffs and shackles when they took him for his shower three times a week – a shower that took place inside bars. He felt like an animal in a cage when the guards pushed his food through a slot in the bars.

As he sat in the Reception and Medical Center (RMC) in Lake Butler, Fla., Gooden’s thoughts turned to a happier time when he was young and his arm was electric and when he appeared to be headed to the Hall of Fame, not these halls of shame.

“I kept looking back to the day I got drafted out of high school [in 1982] and remembering all the joy,” Gooden said. “Now I’m in this little box where two people couldn’t fit in there. You keep asking yourself, ‘What went wrong? What went wrong?’ ”

It is a question that Gooden’s fans have been asking for years. The reports of the former Mets and Yankees star’s legal woes barely faze them now. The story is so familiar, so disappointing.

As he sat yesterday in a prison conference room, wearing a powder blue jumpsuit and black boots, Gooden reflected on his two-decade battle with drugs and alcohol and the jail cell it has led him to.

“It’s been a humbling experience,” Gooden said. “It’s like going from the top down to the bottom. This is the bottom of the bottom right here.”

Gooden, the 1985 Cy Young winner, looks skinny and weathered. He is fidgety and says his stress never stops. His latest bout with the law came after he used cocaine on March 12, violating the probation he received for fleeing an officer last August during a traffic stop. A failed drug test put him in front of a judge in April. He had two choices – a one-year, one-day prison sentence or going back on probation with any slip-up resulting in a five-year sentence. He chose prison.

Yesterday, Gooden said he regrets the decision and that his attorneys did not prepare him for how difficult prison life would be.

That lesson began on April 17 when Gooden went to RMC. He spent 10 days in that one-man cell, never permitted to go outside. He had no contact with his family. He would tell time only by when he was fed.

“I still haven’t recovered from that,” Gooden said. “That was torture. It was like you’re an animal. It was horrible.”

Gooden was transferred to Gainesville on April 27, not a country club but more humane. The campus of one-story, red and white cement buildings does not look like the penitentiaries portrayed in movies other than the high barbed-wire fences surrounding it. In an unbelievable twist, it is the same prison that once housed Darryl Strawberry, Gooden’s longtime teammate.

Most of his days are spent in the drug and alcohol treatment program. In Gainesville, Gooden is not in a cell but is housed in a dormitory that resembles an Army barrack with rows of bunk beds. He arises at 3:30 each morning from his top bunk, eats breakfast at 4:30, then begins his day. The prison has a boot-camp feel. When groups of inmates move from building to building, they march military style and sing cadences.

Gooden has done his best to avoid trouble but he did have to write a 250-word essay after not making his bed properly.

“It’s been the hardest thing I’ve ever went through,” he said. “I can’t say some days are better than others. Some hours are better than others.”

When he arrived, inmates asked Gooden about baseball constantly. He was the No. 1 draft pick in the prison’s softball league, but opted not to play.

“When I first got here I had the shame, the embarrassment, the guilt because of the name and everybody knows who you are,” he said. “These guys are all inmates, too – most of these guys are nice guys – but they’re looking at me like I’m different than them. Because of my background they look at you and say, ‘Man, you don’t belong here.’ ”

Gooden still hasn’t figured out what triggered his relapse. Maybe it was an argument with his fiancée, Monique. Maybe it was the memories of his father’s death that flooded back to him after attending a funeral days earlier. Maybe it was missing baseball as spring training hit full swing.

Whatever the cause, Gooden pulled into a Raceway convenience store on his way home from his mother’s house near Tampa, looking for alcohol.

One beer, he told himself. You can handle it.

The first Budweiser went down quickly. He barely enjoyed it, he was so nervous about being spotted. He began to head home, then turned the car around. The second beer “set him off.”

From the convenience store, he traveled to St. Petersburg to see a cocaine dealer he knew. The dealer wasn’t home on his first visit but Gooden returned. This time, a woman at the house gave Gooden the dealer’s phone number. A few days later, Gooden’s urine test came back dirty.

Gooden had been clean for six months. He had attended rehab for three, and been an outpatient for three more. Today, he regrets not calling his sponsor when the urge to use came over him.

“My problem is, my ego still gets in the way,” he said. “I figure I can handle it myself and I don’t want to bother anybody.”

As he sits in prison, Gooden worries most about his family. He has not been allowed any visitors yet, and the only person he’s spoken to on the phone is his fiancée. He misses his six children and worries what effect this will have on their lives. His oldest child, Dwight Jr., has already spent time in jail for cocaine possession. He tries to follow the Yankees and his nephew, Gary Sheffield, but is only allowed to watch TV on the weekends.

On Mother’s Day, he thought of his elderly mother and what this has done to her. When he last saw her at his sentencing in April, he thought she had aged 10 to 15 years since his latest arrest. Mother’s Day also fell on the 10th anniversary of his no- hitter for the Yankees, the highlight of his 16-year career.

“It was like a double whammy,” he said. “It was a bittersweet day.”

This year is also the 20th anniversary of the 1986 Mets’ World Series championship. Gooden’s face goes lifeless as he talks about not being a part of the celebration planned at Shea Stadium later this year. For him, that season also represents the beginning of his cocaine use.

“I look back at ’86 and I remember when that season was over, that’s when I first got started with cocaine,” he said. “Now here we are 20 years later, the team is celebrating that year and I’m in prison because of cocaine. It’s a sad story, really.”

Gooden could be released as early as November. He is unsure what he will do when he gets out. His first priority is reconnecting with his children and repairing some of the damage he’s done. Before his relapse, George Steinbrenner had spoken with Gooden about returning to his role as a special assistant with the Yankees once his probation officer said it was OK. After his latest embarrassment, Gooden said he would not even ask Steinbrenner for a job.

“I respect him too much to go back to him and ask for a job after all this stuff has gone on,” he said.

He thinks about coaching his kids’ Little League teams or helping out a high school team.

Mostly, though, he thinks about staying clean. He knows people are skeptical, but this time, he insists, will be different.

“I’m tired of hearing myself say I’m going to change and be different,” he said. “Now it’s just actions. All I can say is follow my actions.”

He hopes the memory of prison will keep him straight.

“I can’t come back here,” he said. “I’d rather get shot than come back here . . . If I don’t get the message this time, I never will.”