Post-coital bleeding (bleeding after sex) can occur for a number of reasons, and is nothing to be taken lightly. Usual causes of this condition (if STDs-STIs, such as chlamydia, gonorrhea, trichomoniasis, yeast, are excluded, as you reported) are : Cervical dysplasia (precancerous changes of the epithelial cells that line the cervix), Vaginitis/Cervicitis (inflammation or swelling of the vagina or cervix), Cervical polyps (smooth, red or purple, finger-like growths that grow out of the mucus layer of the cervix or the cervical canal), Endometritis or adenomyosis (endometritis is defined as an inflammation of the endometrium-the innermost layer of the uterus. Both are associated with endometriosis-when endometrium, the uteral inner layer, is placed outside the uteral cavity. Adenomysis is when endometrial tissue attaches itself to the uterus, or another organ such as the ovaries, and grows outside of the uterus), Uterine polyps (when the endometrium overgrows causing these protrusions into the uterus) or Fibroid tumors-myomas (usually benign solid masses made of fibrous tissue). Diagnosing vaginal bleeding after sex is usually a matter of exclusion, thus treatment depends of whatâs causing the post-coital bleeding. You might want to check this issue with your gynaecologist.