(CNN) -- It's understandable to feel stress when your livelihood is on the line, but Charlie Beljan is suffering more than most.
"He kept saying he thought he was going to die," the golfer's caddy Rick Adcox said after Friday's second round of the PGA Tour's final tournament of 2012, held at Disney World in Florida.
"A couple times I thought he might pass out. He just said, 'I'm gonna keep going until I pass out or they take me off.' "
Beljan is fighting to keep his full tour card after a difficult first season on the circuit -- the top 125 players qualify for next season, and he is in 139th place.
The stress is taking its toll on the 28-year-old. He was taken to hospital straight after his round, having suffered increased heart rate, high blood pressure and numbness in his arms.
Incredibly, despite all this he was leading the tournament, which is known as the Children's Miracle Network Hospitals Classic.
"I don't know how he hit the golf ball feeling the way he was feeling," Adcox said on the PGA Tour's official website. "I thought he was going to stop when he heard what his blood pressure was."
Adcox said his boss had been hospitalized last month after fainting on a plane flight, but doctors had not found the cause.
Beljan, who became a first-time father less than two months ago, carded an incredible round of eight-under-par 64 to build a three-shot lead in the $4.7 million event.
The first prize is $846,000 -- and Beljan is determined to play on so he can add to his total of $527,528 from 21 tournaments this year.
"Tour official says Charlie Beljan will play today @ Disney after being taken to the hospital on Friday," Golf Channel journalist Rex Hoggard wrote on Twitter before Saturday's third round.
Beljan told the broadcaster on Friday he hoped it was just a panic attack.
PGA Tour reporter Brian Wacker confirmed the news.
"Doc recommended he not play but found nothing wrong physically. Appears to be anxiety related. Beljan is playing," Wacker wrote on Twitter.
And he played well, carding 71 to take a two-shot lead into Sunday's final round. At this stage he is projected to finish 63rd on the money list.
"I honestly didn't think I was going to get through it," Beljan said. "I just stayed strong."
Beljan had no idea that he was leading the tournament during Friday's round.
"It's nice to be able to walk around and smile," he said. "Yesterday, I was hanging on for my life."