Life is a pleasant calamity for Debi Thomas. From her tenuous beginnings on third-hand skates to her current status as one of the reigning divas of figure skating, Thomas usually has been overburdened, which she deals with by employing her most often uttered phrase, "Oh my gosh, oh my gosh." That can apply to anything from a nick on her blades to her latest bike wreck at Stanford.

In the last year, Thomas has injured her precious ankles, lost her world championship and had her rickety practice rink shut down. These are merely regular occurrences in the career of an athlete who, unused to ease, has therefore never chosen to do anything the easy way.

Told she could not compete internationally and pursue a premedical degree at Stanford at the same time, she has continued to challenge reigning world champion Katarina Witt of East Germany between final exams. In January, on leave from school, she captured her second U.S. title while studying German on her own time, and will attempt to upset defending Olympic champion Witt in Calgary.

Thomas' refusal to follow advice or to respect the tenets of a rigid, almost inbred sport has provided a refreshing interlude in skating. In Thomas, the United States has discovered an unconventional champion with an unsettling perspective, one who greets the Olympics as a splendid but somewhat relieving conclusion to her amateur career, so she can get back to more important things.

"The biggest fear of my life is not knowing what will happen," she said. "I'm scared for the Olympics, I'm scared for the world championships, I'm scared for the rest of my life. As a competitive skater, you dream of the Olympics. But sometimes you also say, it's just a stupid competition."

None of that is to say Thomas lacks the ruthless ambition that permeates this sport. The Olympics will end her contentious rivalry with Witt, a power struggle that has spanned two world championships and two continents in as many years. The score is even, Thomas capturing the world title in 1986 at Geneva and Witt reclaiming it in 1987 in Cincinnati when Thomas skated with tendinitis in her ankles.

The tie breaker will come in Calgary, where Thomas will try to win a gold medal in the same manner she has overcome her perennial lack of money, equipment and time: by skating with her fists. Her intensity is shown by the leave of absence from school for a semester, a first for her. She is trimmer, finally healthy and newly aware of the end of her sometimes bothersome amateur career.

"Ever since the season started I've been so nervous," she said. "It's been like, 'Oh my gosh, this is the Olympics, and oh my gosh, this is my last year.' "

That conviction was lacking in Thomas over the past year, when she described her attitude as "lousy." She developed tendinitis when she overtrained. On iced-down ankles, she lost her U.S. title to Jill Trenary, and was forced to prove herself all over again at the world championships last spring.

In Cincinnati, she managed her long program of five triple jumps without a waver, only to watch Witt do the same, as well as outskate her artistically.

The rematch in Calgary should prove as stirring as the Cincinnati event, which drew standing ovations for both her and Witt. The Olympic meeting is made more dramatic by a bizarre coincidence: Witt and Thomas both will skate to Bizet's "Carmen." So far neither has indicated a willingness to change. "My reaction is that she's going to have to change hers, or we'll both be skating to it," Thomas said.

There apparently will be two vastly different interpretations. Witt chose a more dramatic passage that ends with her mock death; Thomas' performance is brassier. "She dies and I don't," Thomas said. "The reason I don't die is there's no one there to kill me."

Thomas' new choreography came in part from Mikhail Baryshnikov, one of the benefits of her fame. What began as a wishful idea was set up by her powerful managing firm, International Management Group. The dancer and skater met in the offices of the American Ballet Theatre, then had an hour-long session at a Manhattan ice rink in August. Baryshnikov then lent former ABT dancer and choreographer George de la Pena for sessions.

Baryshnikov and De la Pena have transformed Thomas from a somewhat mechanical skater into a more artistic one. In addition to giving her a sort of acting lesson and suggesting she respond more to the expressive music, Baryshnikov told her to "snap it up." He added some ballet arm movements to improve a program that was rather lethargic. De la Pena also improved her leaps, already a strength.

"He's gotten me to open up, instead of just thinking jump, jump, jump," she said.

The result is that Thomas should prove a more relaxed, elegant skater in Calgary, and also one who has finally come to grips with her role as a premier amateur figure. Part of the problem last year might have been Thomas' unfamiliarity with being the center of such attention. Raised in Redwood City, Calif., by a single parent, computer analyst Janice Thomas, and coached by the little-known Alex McGowan, Thomas had been more comfortable as a quiet contender.

Previously her problems were of a different nature, like how to afford the lessons and skates. As a novice, she wore third-hand stock boots, but won third place in the nation in compulsory figures. Janice Thomas worked overtime to afford the lessons with McGowan.

As a U.S. and world champion, Thomas suddenly was exposed to pressures that went beyond cost and expense. Expectations became perhaps unbearable, and finding enough time for everything, always a difficulty, became impossible.

"When I was a nobody it was easier," she said. "When I started to move up the ladder it got more and more nerve-wracking. Now I feel like if I'm going to fall, it's like, 'Oh my gosh, it will be all over the papers.' "

Her mother, who acquired a master's degree while raising two children and working full time, watched Debi slipping. At one point, Thomas was so frustrated by a weight problem that she called home and proclaimed she wouldn't skate again until she had dropped to 70 pounds. Janice told her she had lost her sense of humor and sent her the book "How to Make Yourself Miserable."

"It's a lot of pressure, with all the ups and downs," Janice said. "She'll call and say, 'I don't think I can do this.' She bounces between despair and being overly optimistic. So I said, 'You've got to get this back in perspective. You're not totally alone in this.' "

Thomas' plans are to compete in the 1988 world championships after Calgary, then retire as an amateur and return to Stanford next fall. She is scheduled to graduate in 1990 and, although she will do some professional ice shows, she said her skating will be deemphasized as she works toward her degree, at which time she hopes to open a sports medicine center.

"A lot of things have worked to make my life complete," Thomas said, but she still worries about falling down. "I don't want people to think of me as, 'Oh she blew it.' If I can skate well, people will remember me for a while."