Hi Katejo,
I can understand you not wanting to have Hysteroscopy, although to be fair I haven't had one. All I can say is the first scan was in my local Bupa hospital and the consultant was happy with 4mm and just described it as unremarkable. Today it was in a different clinic by a specialist nurse and she said it was absolutely fine too with 4mm. Could you get a second opinion? I thought it would be so straightforward going on HRT! All my symptoms have gone, its just the bleeding and like yourself it's very light and watery. Im not sure if using the dose is prolonging the bleeding. I started on two pumps gel form Dec 2018 until April 2019 when I increased to three and then increased to four pumps in November 2019.