Low chances of pregnancy but this app has me excited.

I have a 15% chance of pregnancy and I've always been 1-4 days off my period. But I'm now 12 days late and it's just come to my attention.
 "27% chance of pregnancy" I feel like that's exciting even though it's just an app it's not a doctor telling me or a test. 
Heres another exciting fact I've never had to buy a pregnancy test, so the thrill of buying one was almost too much. And the heart attack I had when I seen the price was a bit much! 
Anyways I took the test and it said negative but I'm still happy I got to enjoy that small thrill!