@Wanderingstar16 this is called prodrome, it warns an outbreak is coming. As you’ve rightly noted, the virus lives in the nerve ganglia at base of the spine for genital cases.
The pain is the virus activating and travelling along the nerves.
I also get this down one butt cheek, leg, hips, foot etc.
If it helps, mine was appalling for the first 2 years or so and I medicated daily to prevent outbreaks.
You can be prescribed (either NHS or pay privately) for acyclovir / valacyclovir to prevent outbreaks and therefore stop this.
I paid privately for valacyclovir as I found it much more effective, but it can be costly.
A few years on its nowhere near as bad, far fewer outbreaks sometimes none for ages, and far more manageable. I no longer feel I need to take any medication, apart from some ibuprofen for the nerve pain as and when.
Your immune system should hopefully settle down a bit and get better at suppressing outbreaks.
if it continues to bother you there are specialists in this sort of thing that you can maybe enquire about with your GP?
Im sorry I know how miserable this can be x