I realize this might be because my 1 week old is breastfeeding, but how common is this?

Twice in one day now and second time it looked like a clot the size of my pinky nail.

Update:

Called pediatrician. She said long as there’s no temp, she’s peeing and pooping at least 5 times, and seems satisfied after eating, that I shouldn’t worry.

Asked me about stool and spit up color and seemed totally unfazed by blood in spit up.