Why am I bleeeeding?

Spotted last week pink one night. Turned to brown the next day and has been brown ever since. Only when I wipe and not a ton, sometimes a lil clumpy/stringy. Kind of tapers off later afternoon then comes back. Some cramps on and off, no sex recently.

Abdominal ultrasound showed baby safely in my uterus and at the correct size for 8 weeks with a strong heart beat of 151. Cervix is also closed. Where tf is this brown coming from?