Anal itching feels like it’s coming from inside

I’ve suffered from excruciating anal itching for the last 10 years that only recently spread to my left labia.

I saw a vulvar specialist and they immediately diagnosed me with LS. But the biopsy came back negative. Doctor still feels confident it’s LS.

For those who have this on anus, what does your itching feel like?

My itching is absolutely horrific and feels like it’s coming from inside my anus not just outside.