Hello, Greenish yellow penile discharge with itching after having oral sex is indicative of chlamydial urethritis. Penetrative sex is not always needed to get infected, a partner already infected with Chlamydia may transmit the infection while giving unprotected oral sex. You are suggested to get clinically examined by a GP, get the lab tests (CBC, urinalysis, etc) done to diagnose chlamydial urethritis. Take Urethral discharge culture, or swab test, to rule out gonorrhea. Gonorrhea symptoms often look like the symptoms of chlamydia. It’s possible to have both at the same time. The treating doctor may tell you to do STD test to rule out STI. If tests results are positive you will be treated with antibiotics and antivirals. Get treated at the earliest. Avoid sex for a couple of days. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician