Hi I am on 2mg of Climival which I do believe is estradiol and it does take a while to work, I had my op on the 27th Dec 12 and it is only now in the last few weeks that I can say I feel good, the only thing i can say is every so often I have headaches and I am not sure why, I use to suffer terrible before my op every time I was due on and they feel very much the same but other than slight aches and pains I am ok, hope this helps xx