Ladies: 8 Reasons for blood in your panties other than your period

STDs can be tough to ID. In part, that’s because even if you have one, you probably don’t know it: They often pop up without symptoms. But if you start noticing blood down there, particularly after sex, gonorrhea or chlamydia could be to blame, says Johnson. These STDs—as well as trichomoniasis and HPV—can cause inflammation on your cervix. And when your cervix is inflamed, it can bleed, says Johnson.