I am 5 days late, and getting BFN's!

What the bleep!
I was supposed to have AF on Wednesday July 27th, and I'm yet to have it. I am religiously a 29/30 day cycle girl. My last period started spotting June 26th, and AF started the 27th July.
We had sex, 1st, 7th and 14th of July (he was out of town most of the month)
Today I am 5 days late. I have taken a test on 
Wednesday night - negative
Friday morning - negative
Sunday morning - negative
So confused.... HELP!!!!