Bloody discharge after being checked for dilation

So yesterday I went in to my OB appt and was 37w4d. My midwife stated I was 1cm and 80% dilated. After that I left to the room to go to the bathroom. As I walking to the bathroom it felt as if I was peeing/or pressure I needed to pee. When I was in the bathroom my pantyliner was saturated in bright red blood. I kept wiping and kept having lots of bright red blood. I saw blood just dripping into the toilet bowl. After a few minutes I put a new pantyliner on and spoke with the midwife. I showed her a picture I took of the pantyliner.

She stated that was more than she would expect. That I should go home and monitor it. And to call if it doesn’t stop.

I took about 4 hours for the bleeding to stop. And now I just have slight spotting of brown blood discharge.

Has this happened to anyone?

Why did I bleed?

Thank you in advance.