Hopeful2, it's just about trial and error. You might not be reacting to the estrogen itself, it might be one of the excipients in the cream. Ovestin has chlorhexidine in it, for eg, some have zinc oxide, or other stuff....
Just keep trying different brands or types until you find one that works for you. And there are two different estrogens - estriol and estradiol - so you might be better with one than the other as well.
Blissel is another option, this is very low dose local estrogen gel so might be a gentler starting point...
See if your GP will give you one of each of a range of different things to try, instead of 6 months of one thing - that way you can try them all and see what works best and get more of that.