Hi again IZA
No the womb lining doesn't instantly shrink. In fact I don't know what happenes to a thickened lining if you stop HRT for ever and are post-menopause. I do know (from what I read) that it is thought that the endometrium generally eventually atrophies after some time post-menopause, so that it (the oestrogen receptors) no longer responds to oestrogen and stays thin, otherwise, since we continue to produce oestrogen even when post-menopause but at a low level, our womb lining would continue to thicken. It seems that in some women it does and this is what can lead to cancer. In your case it will depend on how thick the lining was and the bleeding you had. It may well have thinned down?? You will soon find out because if still thick you will start to get bleeding when you take the progesterone (although this may be expected anyway in the first 6 months of continuous combined HRT).
You haven't said what HRT you were using which caused the womb lining to thicken, and how ignorant of the docs then to suggest that you needed to come off HRT if all was otherwise well and no pathology etc, when what is needed is the correct balance of oestrogen and progesterone for your particular body. The fixed dose combi products available are not necessarily right for all women! Also do I get the impression you were taking it cyclically before? if so then the womb lining thickens and thins as part of the cycle so depends when in the cycle the scan etc was carried out.
It does sound like you are one of the women for whom continued oestrogen is so imortant for physical and mental health. I have never tried to come off it for longer than 3 months so I've no idea how I would feel now. I'm in mid 60s btw and you can now take hRt for as long as you want provided there is no compelling medical reason not to. This should be an informed decision between you and your doctor after discussion of the risks of continuing. They should not force anyone to stop HRT. Check out the British Menopause Society statement:
https://thebms.org.uk/publications/consensus-statements/hormone-replacement-therapy/ . As long as you keep yourself healthy in other ways ie body weight, diet, exercise, lifestyle, alcohol etc then you are minimising cancer risk from these sources.
From what I gather you have started taking the oestrogen, and are now feeling better, but have yet to start the progesterone (Cyclogest)? From what you've said already I would not cut the pessary in half but use it all. In fact if you did need a lower dose ( which I don't think is the case with Cyclogest for reasons given before but might be for lower oestrogen doses) it would be better to take it alternate days than to cut it.
I had a brief few months of trying continuous combined hRT when I went back on it after stopping ( 2011) and at the time the doc suggested going for a lower dose so I went onto 25 mcg patches instead of 50 mcg. Along with another woman on the forum on the same combo we worked out that we could take the Cyclogest every 2 or 3 days based on our oestrogen dose and other regimes. For me this worked fine but I was on a very low dose of oestrogen. My gynae specialist gP was happy with this. As it turned out my flushes returned after initially stopping so I had to increase the oestrogen dose, and that being the case I didn't want to take a higher dose of progesterone all the time so sent back to cyclical and changed to utrogestan ( discovered through this forum, as it was quite a new preparation for menopause).
Hope this helps, good luck and hope you continue to feel better

Hurdity x