Has this happened to anyone?

Hi, so I had an IVF start date of March 9th. My period was supposed to come March 4th. The nurse told me to wait and call when I get it. So I contacted her last week to give her an update that it still didn’t come. She sent me to get bloodwork to check my hormone levels. My Doctor had me come in today to do and ultrasound and more bloodwork to see where I am in my cycle. As of today my period is 19 days late. My doctor said that my bloodwork and ultrasound show that I am on day 2 or day 3 of my cycle and that I can start stims tomorrow after a Covid test. How can I be on cycle day 2 or 3 without my period? Has anyone started their IVF cycle like this? I’m nervous that this will effect follicle count,etc. Especially paying out of pocket. Has anyone started IVF without a period?