LP, sickness, and spotting questions

MiniMuff14

I don't get it, I am usually good at predicting when AF is coming.  I have a between 12-14 day LP and I always spot before.  I have had spotting now for three days and am 15 DPO today.  Where is AF??  This was our "take a break" month, because of stress and family reasons so we didn't BD except for 5 days before O and we were protected.  I did just take a test to be sure and it was BFN.  the only other thing I can think of is that I have this nasty cold, can being sick delay AF?  when should I be concerned to call the doc?  I have never gone this long without AF.

 another ?...

does anyone else have experience with spotting before AF.  I tell my doc each time it happens and she just brushes it off...this really concerns me and our trouble TTC .  are there tests that can rule out any issues that have to do with spotting? any advice?

sorry I am loaded with questions tonight! just feeling frustrated!