BFN 13 DPO

How often do y’all know of false negatives at 13 DPO?? According to glow AF should show up tomorrow. I took a test yesterday and it was a BFN. It was a clear blue rapid results test. My cycle was short in Nov and Dec (28 days) but is usually 30-ish days. Today is day 31. Am I holding on to false hope?? Everything I’ve read says that at 13 DPO I should have had high enough levels for a positive test. 😢 (I did use FMU)

I’m waiting to test again until Thursday morning, assuming (hoping!!!) AF doesn’t show.