Hello, have you done any oral sex, using condoms only protect external genitails for some extent, but if you indulge in oral sex (like licking or stimulating female external genitails with mouth or tongue) then your mouth is not protected here.!!! So,, since you are already developed ulcers and already developed swollen lymph nodes you need to be started on antibiotics, no need to worry these infections can be easily controlled and treated, so for this kindly visit dermatologist .