Single ulcer- herpes?

Years ago, I had a single ulcer on my labia. It was tested for herpes and came back negative. Since then, I randomly get one single ulcer at times. It goes away after a few days. It’s back right now and happened to be at the time of my exam. So they tested again and said, again, that it does look like herpes. Now I’m stressing out all over again. WTH?! Anybody dealt with this? Could it be something else? 😩