You have a secret sex cycle: make your lust life soar by understanding your libido's peaks and valley's--plus the days when you're primed for intense pleasure.(Love And Lust)

Ever notice how some days, you're climbing the walls for sex, and others, a frozen yogurt seems more enticing than hopping into bed? Well, you can blame it on biology. While guys have a steady stream of hormones coursing through their bodies that stays generally level from day to day, most women's bodies follow distinct sex cycles that can drastically wax and wane throughout a 28-day period.

"Your cycle marks the rise and fall of your hormones during one month as you move toward or away from ovulation," explains Lisa Masterson, an ob-gyn at Ocean Oasis Medical Spa and Cedars-Sinai Hospital, in Los Angeles. And if you know what phase you're in, you can pinpoint the days when you're feeling especially aroused, which can help you make the most of your sex life, whether you're in a relationship or not. (However, if you're taking birth-control pills, your body doesn't follow the same schedule. Turn to page 156 to learn how the Pill affects your natural cycle.)

Days 1 to 11 Slowly Revving Up

When your period kicks off, your sex hormones are lying low, but that doesn't mean your libido is flatlining. While some chicks are squeamish about having "period" sex, others are up for action. "The drop in hormones that accompanies menstruation relieves PMS symptoms, which leaves some women in the mood for sex because they feel more even-keeled," according to Dr. Masterson. Another reason you might feel randy is increased lubrication. "The extra wetness can make some women feel more sexual," says Bat Sheva Marcus, clinical director of the Medical Center for Female Sexuality, in Purchase, New York. However, from days 6 to 11, you ]nay not feel as horny because your hormones are directed toward building the lining of your uterus and prepping your body for pregnancy.

Passion pointer: If you want to have sex but are having trouble generating tons of lusty energy, kick-start yourself by going into dirty-daydream mode. Fake a few minutes before drifting off to sleep or while lathering up in your morning shower to fantasize about you and your man really getting it on. "Consciously devoting time to fantasizing about sex can help build arousal when you're going through a lull," says sex therapist Laura Berman, PhD, coauthor of For Women Only.

Days 12 to 16

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