Temping during medicated cycles

Hey all, this is my second cycle on letrozole cd 3-7. I am currently CD 20 and got positive OPKs cd 17 and 18. I am also taking estrace to thicken my lining and progesterone as well post O.

The problem is, I am temping and I had a nice temp shift right after positive OPKs and then started my estrace and then my temp dropped pretty significantly.. can estrace make my temp low? Is it even worth it to check bbt during medicated cycles?