Eviepf, I woke up from a pelvic surgery at 38 with the burning, and the urgency. They immediately diagnosed me with IC and I went down that road for a couple years. The IC meds and the diet had no effect on me. When it's bad, it can make you feel so desperate, I know.
What emerged later was that I was in perimenopause at 38. I have one ovary left, and that had "failed" by the time I was 39 or so. So I also then started thinking that maybe my discomfort was VA. Systemic HRT and local estrogen eventually stabilized me so that my flare ups were few and far between.
Another thing that helped was pelvic floor physicial therapy. I am in the US, I'm not sure if you have access to PT where you are. It's definitely something to try if you do.
I took an HRT break and mucked around with my doses from Jan 1 to mid-march of this year, and it caused a terrible flare up. I was burning for about a month. I got my patch dose back up and am taking local estrogen nightly. And this week my pain finally relented! It's back today, but the relief gave me hope.
In my experience over the last 4 years dealing with this, hormone adjustments can take maddeningly long to affect things. When stopping and starting HRT, I often experience a delay in things getting better or worse, which of course makes them hard to track. Please hang in there. I think systemic HRT is a great thing to try, but give it time. Which can be so hard when you're miserable, I know.