Late.. But bfn

My period was due monday 6th july.. But it still hasnt shown up. That makes me 6 days late. I did a test yesterday and bfn.
Is there any chance i could be pregnant? 
I've been having cramps for the past three days and was sure i was about to come on, but nothing..no sign at all. 
Symptom wise, other than the cramps, i'm totally exhausted and veryy emotional! 
I'm so confused about whats going on?!
Has anyone had a bfn after late period and then went on to get a bfp?