How do you no if a guy poped your cherry?

Rupture of Hymen: That is difficult to tell without a physical exam. Typically females have a membrane at the introitus (entrance) of the vagina that incompletely covers the opening (though rarely it is imperforate). During intercourse this is commonly torn and leads to some hemorrhage, which is considered normal. It is impossible to tell from the whether that has happened to you or not. Please see your doctor.