Tiger Woods’ public apology may be the first step toward getting his wife Elin back in his bed, but ultimately the relationship is doomed, sex expert Dr. Yvonne Fulbright said Friday.

Elin Woods is likely to try to reconcile with her husband for the sake of their children, but she’ll never be able to trust him again, said Fulbright, a Fox News contributor.

"Not to be a pessimist, but the reality is, this is so huge," said Fulbright, whose latest book is "The Better Sex Guide to Extraordinary Lovemaking."

"At the end of the day, you can’t teach an old dog new tricks."

Woods admitted on live TV that he cheated and he was "deeply sorry" for his multiple extramarital affairs. He said his wife felt his apology needed to come in the form of his behavior, and not in words.

"There’s a lot going on here, only they really know the true reason behind his actions," Fulbright said of the couple. "And he may be just learning those reasons in therapy. He needs a tough therapist who will hold him accountable and who will call him out on his narcissistic and arrogant tendencies. Their success will come down to not how much he’s sorry or how much she can forgive him, but if he’s willing to change. Can he be in a monogamous, faithful relationship?"

Dr. Ian Kerner, a New York City-based sex therapist and author of "Sex Recharge" said Woods fits all the signs of a sex addict.

"Tiger does fit the sex addict category because when you look at the sheer number of mistresses, the quantity, unprotected sex, and sex in places where you could be discovered, exhibition sex — it was out of control," Kerner said.

Woods made the right choice in admitting himself to sex rehab, he added. Woods said Friday he would return to therapy on Saturday.

So what exactly goes on behind the closed doors and seclusion of sex rehab? This is a gray area to most of the public, which only adds to the scandal.

"Sex rehab is based on the classic 12-step program, a combination of group therapy, cognitive behavior therapy, and looking at what triggers are, psychoanalysis," Kerner said. "A big part of going is being placed in an environment where you are not exposed to triggers. No Internet, erotic materials, access to anything that might trigger arousal."

Addicts who abuse drugs or alcohol need to forgo their addictive substances forever. So does this mean Tiger has to practice abstinence?

Kerner said this is not the case.

"If you’re an alcoholic or drug addict, you can stop and go cold turkey. A sex addict has to be able to return to sexual activity," Kerner said. "Tiger Woods needs to have sex again, he is going to have sex again."

The major healing factor for a sex addict is to change the way he thinks about having sex.

"The key is that he needs to associate sex with emotions, not the ways he has been looking at it. Developing bonds and using sex as an expression — program him to use it as intimacy, not gratification," Kerner said.