why am I bleeding brown blood?

As you can see I've had my period not too long ago and I'm supposedly in my fertile window. Yesterday when I wiped I had a small amount of light pink blood and then through that night I had a small few drops of brown blood on a panty liner. I wiped and had nothing. so earlier today I wiped and had a bit of brown blood and used a panty liner. Only a small streak was on it through the whole day. Anyone know what it could be??? I've never bled unless I've been on my period.