This might not be helpful as I don't have thrush, but I had no idea that vaginas/vulvas needed moisturising. Like basic moisturising, whether you use vaginal estrogen or not. It sounds obvious but it wasn't obvious to me, and all that itching, thinning skin and so on can be so sore. I use coconut oil (organic), which was recommended on here but if it's all very inflamed, something more specialist might be better, although I find this completely neutral and cheap. It makes a big difference in comfort for intimacy, even walking around.
There are also devices increasingly used for vaginal atrophy as well as pelvic floor exercises to build muscles.
I think they have to be used in conjunction with the treatments suggested, but I agree with everyone that you need to get a second opinion and test for anything else, the GP may be running out of options or not aware of the latest thinking on the issue.
Once you truly know what it is, the treatment pathways will be more obvious. I do think though it's a shame we don't get educated on vaginal atrophy before it gets bad, as there are quite simple things you can do that at least stop the decline, and then treatment options if you run into more serious problems.