I had sexual intercourse with someone who was tested negative. We has intercourse roughly for about 3 hours, and a few days later I noticed what seemed like ulcers on my buttocks and on my labia. Now, a couple more have appeared. The one s on my labia are small, and the two on my buttocks are about 1 centimeter in width. All have a white center. The ulcers on my labia first appear blister like, then appear like a small ulcer. They burn when urine drips onto them. What might this be? Is this pressure sores or a bacterial infection?