Hello
Estrogen have a beneficial effect on the quality of cervical mucus so increase cervical penetration .
But you were a patient of
breast cancer some 4 years ago and use of estrogen is contraindicated in breast carcinoma .
You didn't mention your age as it is important in this case .
Why , you want to use estrogen cream ( however, you mentioned that your wall of
uterus is thin)?
If you have completed your family planning i.e .
pregnancy , if require pregnancy , you can use this cream . But if you don't require baby then why this cream . In that case opt for other option for thinning of uterine wall .
2nd point is about sex , you can do it after successful treatment for thinning of uterine wall .
However , I mentioned a complex mixture of things but it was important for your point of view.
So consult a gynecologist and get his opinion .
Good luck.