Libido Menstrual cycle 

Women's libido is correlated to their menstrual cycle. Many women experience heightened sexual desire in the several days immediately before ovulation.

Causes of low libido include not getting enough sleep, unresolved conflicts within the relationship, & suboptimal amounts of testosterone in the body.

Libido has been associated with the menstrual cycle because the level of testosterone changes according to it. During a month, testosterone levels rise & fall & that affects the woman's interest in intercourse.

According to the founder of Hormonology & the author of '28 Days - What Your Cycle Reveals about Your Love Life, Moods, & Potential', Gabrielle Lichterman, women are most likely to have an increased interest in sex from the 1st to the 14th day of their menstrual cycle & from the 24th day to the end of their cycle. This is mainly due to the fact that in these days the levels of testosterone are the highest. In the first 14 days of the woman's menstrual cycle, the levels of testosterone rise gradually which makes their libido increase consistently prior to the ovulation. The 13th day of the menstrual cycle is considered the day with the highest testosterone levels. The week after the ovulation, the levels of testosterone are the lowest & as a result, women will feel less interested in sex during those days. Moreover, the levels of progesterone increase during this week & this leads to a difficulty in achieving orgasms. Although the last days of the menstrual cycle are marked by constant levels of testosterone, women's libido might boost as a result of the thickening of the uterine lining which stimulates nerve endings & makes a woman feel aroused. Also, during these days, the estrogen levels are also declining, resulting in a decrease of natural lubrication.