I am so sorry you are having this side effect - strange that you had it with Arimidex as well as Exemestane! .... Nausea 'is' one of the side effects but I was lucky & didn't have it. I was only on Arimidex for 6 months before swapping to Exemestane & was on that for over 6 years with no nausea, just the usual aches & pains.
When do you take the tablets? I used to take mine at night. Can you change it to a different time & see if it gets better?
Do you take them before or after a meal? Maybe Swap it around.
Are you taking the 'actual' tablets, or one of the Pharmacy 'copies'? Some of the copies use a different coating on the tablet - which might affect you adversely.
Are you on anti-inflammatories at all? I had a major liver function fail when I was put onto Mobic for a hip injury! My liver almost failed!
Have you had an 'uppie & downie' (colonoscopy/gastroscopy) in recent years (or ever had them??) If this nausea persists, I think it would be wise to ask to have them done, to make sure there are no issues down there.
Acid reflux is often a problem associated with gut issues - and the tablets you are on only 'mask' the issue, it won't fix it. :(
I've put a brick under both top legs of my bed, putting it on a very slight 'angle' (not enough to interrupt your sleeping) but enough to stop the stomach acid from going up into your throat! I have regular uppies & downies too very 5 years.
Take care & all the best xx