Hi
As far as I'm aware, that should be no reason to stop hrt.
What treatment have you been offered for the stones - are they able to be broken up via ultrasound, for example? Or is surgery your only option.
It might be worth your while emailing Dr Currie for £30, to get some advice from her? Then you can print it out and take it to show your gp and go from there.
Although I don't have personal experience of this, there are many ladies on here who have, and I'm sure one of them will be along to give you more info.
Good luck with it all xx