OP I had similar a few years ago. And it turned out to be herpes. In my case, it was HSV1 but transmitted to the gentials, which is apparently unusual. Hsv2 can lay dormant for many years, it isn't an indication of adultery.
My GP would not allow my results to be given other than by him. He wanted to speak me through it, check I was ok, tell me protocol on future attacks, on partners, on telling previous partners , safe sex etc. It was a horrible, scary, emotional, time.
But I can honestly say three years on (and a handful of further attacks) that it is ok. If it is herpes, it is not the end of the world. It is liveable, it is manageable, it is ok.
Yours may be a reaction, it may be an allergy. But I remember those horrible days of waiting for the swabs, and wanted to give you a hand hold. My thread was on here back then, but tbh it may have been on a 30 day chat deletion.
What has DH said?