Bleeding mid cycle negative OPK

Abby

This morning when I woke up I had so much watery (I guess) CM. I mean it was going down my leg! Well this afternoon I went to the bathroom and noticed i had bled. It wasn’t full blown AF but it wasn’t just light spotting. It was brown in my underwear. I thought maybe OPK but i took one tonight and it was negative. What’s going on? Here is my cycle as well.