Hi, Welcome to HCM. Oral sex carries a very less risk for both HIV and STD. Herpes simplex infection will have the eruption of multiple tiny vesicles going into multiple tiny grouped ulceration. This is a self limiting disease and will heal even without specific treatment within two weeks in a normal immuno-competent individual. Uniform redness of penis and burning urethra are not symptoms and signs for Herpes. Gonorrhea, Chlamydia, and Syphilis through oral sex is extremely rare. Yeast infection is quite possible following a oral sex as yeast a commonly present in saliva or mouth cavity in many people. It can be easily confirmed with some investigations and can be treated with anti-fungal antibiotic creams and if necessary oral anti-fungal tablets. Drinking plenty of water will improve the burning sensation of urethra. Simple urine examination will reveal if any pathology in urethra is there or not. Get well soon. Dr S.Murugan