5&1/2 weeks & spotting red then brown

So I’m right around 5&1/2 weeks according to my LMP. Last night when I got out of the shower I wiped & it was pink then there was some bright red blood. I was convinced I’d wake up with a miscarriage but when I woke up this morning there was a tiny bit of red blood but on & off small brown spotting the rest of the day.

I got an ultrasound that showed a gestational sac with a yolk sac but indefinite fetal pole yet which may be due to me being early. Nonetheless what was the blood from? If the gestational sac and yolk sac are in tact & sitting high was it not the beginning of a miscarriage? I don’t go back to the OB until Thursday and I’m so perplexed.