Hi Pippa, I'm in a similar situation & it's an utter pain

. On oestrogen only following hysterectomy 2+ yrs ago & have been on HRT for 10 years, mostly at higher doses than now. I reduced to 30mcg 5 months ago to try to work out which of my current symptoms are due to side effects, which still a likely consequence of menopause & which possibly due to other chronic conditions & surgical legacies.
In mid-60s, my sense is my body has become less biochemically agile if you like & is now struggling to process oestradiol efficiently. A worry as I am underweight with osteopenia so had really hoped to be able to continue on at least a 50mcg dose for bone protection. That said, any oestrogen replacement should help & at this age I need to be pragmatic rather than idealistic & concentrate on improving QOL.
Main issues are chronic insomnia due to intense overheating with horrible associated adrenalin/cortisol reaction of pounding heart, irrational anxiety & nausea, v frequent feverish nightmares, sluggish digestive tract & fluid retention, both the latter causing v uncomfortable bloating with knock on effects on bladder & bowel comfort & function.
With somewhat inconsistent response to the reduction in dose, in uncertainty & frustration I've gone back up to 37.5mcg a couple of times, but each time have definitely felt worse on the higher dose within a few days.
Still a work in progress, but I consistently find that fluid retention & digestive issues (& the horrible consequent bloating) improve within 10 days or so on doses <37.5mcg. Overall 5 months on, sleep seems somewhat better on the lower dose but it varies from night to night & there's still some way to go to get to a stage I'd say is adequate.
Atypical hypothyroidism is one condition in the mix muddying the picture for me, so assuming your situation is more straightforward I'd really hope you would feel more consistent improvements sooner.
W x