you may be used to hearing about the female orgasm from women's magazines rather than scientists, but researchers are slowly beginning to study it - and often contradicting the advice columns. Part of the problem, they say, is that the female body has been studied far less than the male body and is far less well understood.
"I call it the ring of fire. It felt like fire in a circle in between my legs and that was a constant feeling - it was burn-y itchy, and then with intercourse or even a tampon it was like a serrated knife, very painful."
Callista Wilson, a San Francisco fashion stylist, first experienced this when trying to use a tampon at the age of 12. She was in her 20s before she finally saw a doctor.
"She seemed extremely puzzled that anything would be wrong," Callista says. "She said: 'You look perfectly normal so I would suggest you go to a therapist to talk about whatever's causing you this pain, it must be in your head.'
"She seemed extremely puzzled that anything would be wrong," Callista says. "She said: 'You look perfectly normal so I would suggest you go to a therapist to talk about whatever's causing you this pain, it must be in your head.'"
Image caption Callista Wilson consulted 20 doctors before her problem was solved
And it was another 10 years before Callista got a proper diagnosis.
Her sexual problems during this period affected every aspect of her life, she says, leading to depression and the breakdown of her relationship. Finally, after seeing 20 doctors, she found herself in the waiting room of Dr Andrew Goldstein, director of the Center for Vulvovaginal Disorders in Washington DC.
He told her that she had been born with 30 times the normal amount of nerve endings in the opening of her vagina - which meant that when her vagina was touched, it felt as though it was being burned. The solution was to have a circle of skin at the opening of her vagina removed. Once that was done, she was able to experience pain-free sex for the first time.
What is 100 women?
BBC 100 Women names 100 influential and inspirational women around the world every year. We create documentaries, features and interviews about their lives, giving more space for stories that put women at the centre.
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