Estrace cycle days 1-12 to thicken lining?

My first injectable cycle looks like it will end up not working because my lining was super thin. My doctor wants on my next cycle to have me take estrogen cycle days 1-12, come in for an ultrasound and if my lining is thick, start me on provera for 10 days to bring on a period and THEN start my injectable cycle again. I should have asked but I’m kind of confused-won’t starting provera and getting a period just shed the entire lining anyway? Anyone else done this??