18dpo - 4 days late - negative pregnancy test

Hello, I’m 33, I’m usually a 25 day cycle but I’m at the end of being 4 days late (period is usually 4 days), I did ovulation testing and I know I ovulated 18 days ago. Taken 3 different types of pregnancy test (just to make sure) and all completely negative no faint lines or anything. I’m usually like clock work but my cycle has varied by 2 days once (was skiing so thinking that was altitude thing)

Came off birth control in November. Has anyone else had this?