I really liked the user friendliness of Lenzetto but unfortunately it is very weak. It also gave me IBS symptoms. Despite using three sprays, I only managed to get the same blood levels of oestrogen as one pump of Oestrogel.
I think you are probably feeling unwell because your oestrogen levels are far too low. From what I have read on here, Sandrena is not always well absorbed either so it might be worth trying Oestrogel.
You don't need to break between different types of oestrogen, in fact, I would avoid it because your levels will drop too low and you will feel worse.
Poor absorption is a common problem I'm afraid, do you know what your levels were when you had blood tests?
If it's easier, I would try increasing the Sandrena if you have plenty of it and also add in one spray of Lenzetto good measure. If you haven't felt any improvement after 7 years of HRT and you have brain fog, it does suggest chronic low levels of oestrogen and it would be worth getting your blood levels checked. It sounds like you have been bumping along all this time on an inadequate dose.