Hello You are taking sulfamethoxazole+trimethoprim , that s right but this never causes any vaginal discharge , however, in few cases this causes hypersensitivity reaction so this may be the cause of vaginal irritation . But this allergy ( irritation occurs on day 1-2 as you start this drug ). These are symptoms of genital herpes simplex : Can be asymptomatic , subclinical , mild or severe. Incubation period 2 to 12 days . painful vesicular lesions/painful ulcers and tender lymphadenopathy occurs. Lesions are usually multiple. Can cause urethritis and cervicitis , which can not be distinguished clinically from chlamydia and gonorrhea . Diagnosis can be confirmed by culture ( gold standard ) , highest yield with vesicular lesion ( as from vaginal swelling ) PCR Type specific serology cytological changes. So in my opinion don t think so and at once consult a dermatologist and get his opinion. Hope this will help you. Milky yellowish discharge is due to infection ( cervicitis amy be the reason )