Someone tell me about this blood.

Katlyn • 1 son born july 9th 2016! now expecting eubanks baby #2
So it's 8 days until my next period according to this app, and I've had some random bleeding today and last week sometime while I was ovulating. I figured the first amount of blood was mid cicle bleeding. But this little spotting is new lol. The first time was all day. And now it was just a little bit like a few minutes. Why?