If you have HSV2 genitally ...

the virus goes dormant in the sacral ganglia near the base of the spine. The area you are describing may be a bit outside the dermatome (skin area) that the sacral ganglia serves, depending somewhat on the individual. Certainly by the time you get to mid-back it's beyond the sacral area, which is generally described as the "boxer shorts" area.

That's a long way of saying that I doubt it's due to genital herpes, but then I'm not a doctor, so don't take my word for it.