Is there a problem if you have yellowy/brown discharge after sex? (mixed with the semen?)

Can not tell : Unless culture is taken from discharge . Your doctor can take a swab from the discharge .

Vaginal discharge: Vaginal discharge requires an examination to determine the cause and treatment. Bacterial vaginosis is the most common cause and often has a vaginal odor. Vaginal itching can be a sign of a yeast infection. Sometimes vaginal discharge can be a sign of a sexual transmitted infection. Testing is important to determine the treatment and keep you and your partner safe.