Hi Floral
You need to give changes in dose more time for your body to adjust, especially changing from tablet to patch. If insufficient oestrogen was the cause of your symptoms, depending what they are, eg sweats and flushes, then you should notice the difference very quickly. Other symptoms take time.
100 mcg is a pretty high dose for someone of your age if you are absorbing it. You've gone from a medium dose (2 mg tablet) to the upper end of high, with 100 mcg. Chopping and changing won't really tell you what's going on. I am surprised that you were put straight onto 100 mcg because usually the advice is to increase graudally - though obviously in your case as you are changing delivery method then it's not quite so straightforward. Is this an NHS specialist at a menopause clinic?
In your position, personally I would persist with the 75 mcg for a few weeks and see how you feel, if you felt some sort of improvement?
The other thing is if your appetite is poor then this sounds like it has nothing to do with hormones - and maybe something else going on? If lack of appetite persists I would definitely consult a normal GP.
Low energy - apart from the usual reasons, a bug, or inadequate vitamins or minerals (iron, vit D etc) - can also be caused by low testosterone - if you also had your ovaries removed when you had your hysterectomy. Have you ever been offered this as well as oestrogen?
Hope you manage to get this sorted so that you feel better soon
Hurdity x