Hello Adnival! Nice to meet you!
Your hot flushes and lack of sleep sound grim. Not an expert but I'd guess the difference between your symptoms and your twin's is that you've got no oestrogen at all (no ovaries) whereas she might have just a bit to keep her going. Even more not of an expert on this but there are some lovely people on here who also had early hysterectomies or ovarian failure and I'm sure someone will be along soon on that.
If you're really suffering, you could go back on the HRT?
Anyway, you'll find lots of companionship here. At least we all know what you're talking about.