It used be that if a woman's hymen was broken that would be the tell tale sign that she was not a virgin. However, for some women who are very athletic, the physicality of sports can cause a break in the hymen.
Hmmmm that means girls and guys are the same no one can or will ever know if any one is a virgin
No Dave, no doctor can simply examine a woman to tell if she has had sex before unless she is pregnant or has a sexually transmitted disease, there is no way to tell by a routine exam.