Hi Trixiebell, I have been there too (well, still am!). I have had three hysteroscopies and, at the last one, my endometrial thickness was 7.9mm and was absolutely fine. I had an endometrial biopsy taken, which showed no issues. The gynaecologist said that, when on HRT, the womb lining can be as thick as it was during menstruation years.
However, it’s always best to get it checked and I can tell you that the hysteroscopy isn’t pleasant but they will give you lots of pain relief. My hospital, Birmingham Women’s give you gas and air too. It’s over quickly and really isn’t that bad. Let us know how you get on