How to E/T?

Hi everyone. I have hormonally mediated vestibulodynia, I think caused partially by being on the mini pill for 2 years (I stopped 3 yrs ago, and the discomfort started then). Doctors have been, as everyone else here has mostly echoed, not much of help.

I convinced a doctor to get me estradiol cream, which has been helpful, I apply it once every 2 days. I'm not sure how much it is helping for the long term. I have heard people say E/T cream is the right move for this condition so I would like to try- what's the right way to start using?

The thing is, after my period- and up until 2 weeks before, I have minimal symptoms. During pms is when the flare up happens, and it's bad. Do I start using the cream only when I feel the itching (during flare ups), or even when I don't feel flareups? Thanks.