To be or not to be ...pregnant. What shall it be lol

Natasha
According to this app and a few others that I have I unknowingly had sex on one of my fertile. I have yet to get my period and I am 18days late.
I have taken a few test and they came back negative but like I said I have yet to get my period. I am not on any medication or anything that would effect my period and have not been overly stressed about anything. Also, the first time I got pregnant I received  a bunch of false negatives. It wasn't until I was maybe 3months that I got a positive. 
8days left in the month waiting to see if I get my period or not.  The waiting is going to kill me lol 
Has anyone ever been this late with their period? So far I've had a very steady cycle of 36days and all my apps add up to the same prediction date for my period.