Oh dear! Taz
. It's all a bit of a mystery really what everything is due to. I still think that some of us need a much higher dose of oestrogen to give us that feel good factor - I know in my case for example that I feel flat a lot of the time (but much better in the summer!) - not depressed or anything but just lacking in oomph like I did when I was fertile.
However replacing this through HRT obviously isn't the whole picture - after all our endocrine system is complex and all sorts of other hormones that we barely know anything about also milling around so HRT only approximates this! Not only that we all react differently to replacing it through HRT and added to that if you've had a hysterectomy this may also affect the impact of added oestrogen.
Did you actually try the 75mcg oestrogen? In your position if you are still feeling low on the 50mcg I would be tempted to try it for 3 months after getting used to the 50 mcg again just to see if I felt better - as you don't need any progesterone, but this may not do the trick!
The weight gain is not so good though - I can understand your not being enamoured of this! I have to be permanently on quite a strict diet to keep my weight down - but not sure if this is because of the HRT, thyroid, age or what!
Anyway as you say it could be coincidence but you can't really know - at least I hope you feel better overall back on the oestrogen - that's the important thing - and to protect your bladder etc
Hurdity x