Hi Tumbleweed
You've already had some good replies on here. I'm just a bit older than most of us on here - there are a few of us who are er... a bit long in the tooth ! So have read quite a bit over the years, and tried various types!
Just to pick up on a couple of points.
Re progesterone withdrawal - yes that's a thing, and is a major component of classic pms (reduction in oestrogen is the other) - so most women during their menstrual years will experience it to a greater or lesser extent ie headaches, irritability, low mood etc. Your withdrawal symptoms are just more severe than most for which I sympathise. And yes you should be through the withdrawal within 3 or 4 days - it doesn;t hang around in the system for long enough.
Once it leaves the system, then if you are post-menopause, you should be on an even keel and enjoy the benefits of oestrogen only. If oestrogen is at the right level to eliminate flushes and sweats, and sometimes a bit more just for the feel good factor, there should be no issue with sleep, unless other factors are at play?
However I have no knowledge of the GABA scenario. What I do know is that taken orally is very different from taking vaginally because oral intake creates a large amount of different metabolic by-products ( because it goes through the liver and digestion) compared with vaginal intake, and I think some of these have affinity with GABA receptors and are responsible for some of the adverse side effects of utrogestan.
Re the sedative effects - yes it can act a bit like a "drug" in this respect, and especially at the quantities needed to protect the womb, because it has to be taken at higher doses than would normally occur in the body ( apart from pregnancy) when the ovaries send out bursts of smaller doses on a much more frequent basis - so I understand. So some women with sleep problems like this effect - and you seem to be one of them.
Me - I HATE it because it makes me dopey, sleep far too deeply and I feel constantly tired for the whole time I'm taking it.
In your case it's a question of taking the least bad scenario - a long cycle would stop the permanent progestogenic side effects. but you would have to suffer the withdrawal. If your sleep is still affected for the whole time on oestrogen only - say for 4 weeks, maybe the dose is wrong or there are other factors affecting your sleep? Taken every day as you are doing - you'll get the sedative effect but will have to put up with feeling below par all the time.
By the way like Penguin - I taper off my progesterone when I can, with 100 mg for say 3 or 4 nights at the end and this definitely reduces the impact of withdrawal. I only ever use it vaginally.
Cyclogest only comes in minimum size of 200 mg - I can't imagine cutting them at all as they are tapered at one end to facilitate insertion ( if they are the same shape as they were years ago - I haven't used them since 2011). It's not licensed for HRT though some docs ( and many specialists) will prescribe it, ditto Lutigest.
Progesterone cream should not be used for endometrial protection. It's not strong enough nor regulated.
Hope this helps and hope you manage to resolve your dilemma!
All the best
Hurdity x