Clomid can also make you have higher estrogen levels, so maybe that is what your doc is thinking as far as
clomid thickening your lining. If lining is thinned due to
clomid side effect, then
estrogen supplement won't help (that was the case with me).
Although my lining was very thin on 1st cycle of clomid, my RE had me continue 3 more tries with clomid, saying that lining responds differently every time, and they wanted to establish pattern of thin lining.