Hi SammieJane- re hair loss. I too have suffered from this and find it deeply upsetting. It started I think in perimenopause and I didn't notice a big difference until probably a year after I had been on various combined HRT regimes. I came off it briefly and then back on patches and Utrogestan. As you know, oestren is generally considered to promote growth, progesterone can make it worse. I understand that you only take oestrogen.
I eventually went to a trichologist who diagnosed telogen effluvium, started me on iron and vitamin D supplements with a scalp spray ( after a few months ) and it has helped with regrowth.
HOWEVER, my hair volume and density will never go back to what it once was. It's difficult to get your head round this, there are things you can do to help, but the long and short of it is that some women are either genetically and or biologically disposed to it and others aren't. If you look around you will see middle aged and elderly women with great hair, some will be taking HRT , others not . A significant number ( around 40-50% ) will experience thinning and hair loss. Some of this will be easier to treat than others.
I sense that you are driving yourself crazy trying to figure out what is causing this so you can take steps to rectify it. I'm not certain that you?ll find definitive answers to this. We are all different and react in different ways.
It's taken me a long time to reach this conclusion, do what I can in terms of addressing the problem, indeed ,even accepting it. Ultimately I think it's the luck of the draw.