Help! Getting anxious due to symptoms

I had moderate cramping like a bad period yesterday all day with some initial pink spotting, then red, now brown. Haven’t had another hcg to compare changes. But had an ultrasound today which showed the yolk sac. I just found this when I went to the toilet.. what is this!?! I’m becoming increasing worries. I’m 5.4 weeks

After some feedback on other people’s experiences? Thanks