false pregnancy test?

Aubree
So I am 2 weeks late now.. 
my period was suppose to start. Well I keep checking the app and it still isn't coming. 
I've taken 3 pregnancy tests over the past 2 weeks. Like ,2, 2 weeks ago and 1 last Monday. 
Suggestions? Help?
We aren't necessarily trying. Nor are we preventing. However, I not sure how to take this.
Before anything else, I'm not diabetic, nor stressed, or changed anything about my routine really. 
Last period was on time but short.. 
HELP!