Letrozole and no period

I’m pretty late on my period but all pregnancy tests are negative. I was prescribed 2.5mg of Letrozole this cycle. I ovulated on June 17. I can’t start the next dosage of Letrozole 5mg until I start my period. Why is my period non existent! I also only start bleeding if my doctor puts me on 10mg of progesterone for two weeks. The first few days of taking progesterone I start my cycle. Which that is suppose to do that opposite.

Has anyone had anything similar happen to them?!