Sore on labia majora

Patient: I have a sore or ulcer on my labia majora.About 5 months ago I had an outbreak with a sore, ulcer, rash and blisters on my upper thigh and labia majora. The doctor immediatly concluded with herpes, but tested me for all STD’s. All the tests came back negative, including the IGG for herpes, but a week later the IGM came back positive. At this point I hadn’t had sex of any kind for over 6 months, so since the IGG was negative he concluded it to be herpes zoster (shingles). All the rash and blisters were on my right side ONLY.Now 5 months later I got a small sore on my LEFT side on the labia majora. It is only a few milimeters big and it is not itchy or painful, but a little uncomfortable. I can walk, sit etc without pain.I have had sex a few times in the past 5 months, but only using a condom.What can this be? Is there any way this can be anything else than an STD?I am 27 years old and female