Hi Lynne - I can see that it is a worry having investigations because the mind always suspects the worst, but really good that the the standard is to check women out whenever anything happens that is different from the majority.
I can't remember if you are on HRT and having a cycle still?
I have to go for a hysteroscopy and biopsy next week ( also possible polpyectomy) because my lining was 7.4 mm after the scan. However I did read that with a cycle the lining can vary by up to 3 mm over the course of the cycle so part of your build-up may be due to that.
Whatever reason it does need to be shed so once they've found out whether you've got hyperplasia or not, they may we give you progesterone to reduce the lining.
Do take care - try to keep calm and find something to take your mind off things if you can. Hoping you receive reassuring news in a few days
Hurdity x