10dpo Letrozole/Femara pink spotting. AF early on letrozle anyone?

Al
AF is due 10/21, today 10/16 I started spotting pink in my CM. Have cramps and had severe diarreah and vomiting 9dpo (had to go to the ER to get meds and fluids through IV). Still feel a little nauseous today but just feel the cramps and the spotting now. Anyone experience AF coming early on Letrozole? Btw I have PCOS.
Anyone had similar experience?