help??

Madison
I'm hella stressed right now because of the way my period is going. It's usually never irregular (other than like, 3 cycles). 
I'm 12 days late. Only had sex once between my last period and now, and it was like, right after my last one ended. I don't believe we did anything for me to get pregnant, but it still worries me and my anxiety is messing me up. <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a> is telling me my "chance of pregnancy is 7%," but I don't know how in the world it would know other than symptoms I've logged. 
I took a pregnancy test 2 days ago, came up negative.  
Any advice or help??