Prometrium confusion

I am taking prometrium as a little extra insurance after my IUI. I have read it is to thin the lining of the uterus...I thought I was on it to promote the lining. I am also wearing an Estring for the lining. Are these two meant to work together? I am confused.

Prometrium is a form of natural progesterone or/and progestins which role is to maintain the integrity of the uterine lining, to prevent cellular growth. Progesterone and progestis are important for woman to take when they are taking the estrogen product. Progestins work by causing changes in the uterus, after the amount of progestins in the blood drops the lining of the uterus begins to come off and vaginal bleeding occurs. It also helps pregnancy to occur during egg donor or infertility procedures in women who do not produce enough progesterone.
And as the matter of Estring, it’s the product that treats both vaginal and urogenital symptoms of Urogenital Atrophy (UGA). It is an estrogen replacement system for relief of the vaginal problems that often occur after menopause, postmenopausal urinary problems etc.
The combination of these two products is good, as it’s good to take estrogen when you are taking progesterone but you don’t go out of limits of the recommended doses, if you have any further doubts, feel free to ask!