40 days late. what is my body doing?!

Dr
I'm officially 40 days late. Around 27 days I thought I started, but it was just spotting. 
I've never been this late in my life -- and yes, I took a pregnancy test. BFN. I have an apt Monday morning for my annual so I'm hoping to get an answer then, but til then, anyone else ever had an issue like this with their period? Should I worry?