Hello, They are small, painful sores in the mouth. They are recurrent and runs in families. They are small or larger and sometimes you may get Herpetiform ulcers which are multiple and very painful and not contagious. These are common in women. Usually they are triggered by accidental biting, over vigorous teeth brushing, a sharp tooth, anxiety and stress, during period, stopping smoking, iron deficiency, coeliac disease, Crohn's disease, beheet's disease, HIV infection and sometimes medications. They are seen inside the lips and cheeks, floor of the mouth, under the tongue, round or oval in shape, whitish in color, inflammation around the edge. Usually causes pain especially during eating and drinking. At the same time get the full blood count, Vitamin B12 level, iron level, ESA. If the ulcer is present more than 3 weeks and very painful than you should see your Doctor. Treatment consists of avoiding hard or irritant foods. Get yourself checked with a dentist or a doctor and also use an antimicrobial mouthwash or a spray if the ulcer is very painful. Keep your stress level as low as possible, eat a healthy diet, avoid any food which can trigger mouth ulcers, have regular dental check-ups with a dentist. You also mentioned that you had oral sex (unprotected) and you were tested for Gonorrhea and chlamydia which come out as negative. If it is still bothering you, you can consult the dermatologist and allay your fears. Thank you.