Found this article hope it helps.
A guy can tell if it's a girl's first time, only if she has a hymen
the thin skin that may stretch across part of the opening of the
vagina that makes penetration difficult. Many girls do not have
enough hymenal tissue to make it difficult. That's why it is not
possible to tell whether or not a girl is a virgin by examining her
hymen.
A girl may bleed if her hymen has not yet been stretched open. Some
girls stretch their hymens before intercourse during sports or
other activities, such as horseback and bicycle riding or through
insertive masturbation.
