Dr. Laura Berman on why people don't talk about sex.

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Research shows that more than half of men and women are unsatisfied with their sex lives and one in five couples are in sexless marriages. Dr. Laura Berman, a sex therapist and the founder of the Berman Center for Sexual Health, uses talk therapy to help couples build stronger relationships and improve their sex lives.

Dr. Berman says problems in the bedroom usually stem from communication issues. "Nobody knows how to talk about sex," she says. "It's partly lack of information and it's partly lack of comfort. No one's really addressing the issue. They just kind of sweep it under the rug."

One mistake couples make is that they think sex should happen naturally, Dr. Berman says. But that's not always the case. "Especially if you're in a long-term relationship, you're always going through ebbs and flows physically, socially and environmentally," she says. "You can't expect everything to be working perfectly all the time. You've got to fine-tune things along the way."