Day one of ovulating and bleeding

Hello,

Today according to <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a>, I am day one of ovulating in my fertile window, but today I also woke up red blood in underwear and back hurting?

I'm not sure what this bleeding is as I finished my period a week ago, does anyone experience this or have any advice?