Spotting and One sided cramping

Monday was having a little bit of brown/pink spotting (which I have read is a totally normal first trimester thing), but then I started having some pretty painful cramping only on one side. Called my midwife and got an ultrasound done. According to the ultrasound I have a gestational sack and a yolk sack but its too early to see a baby in there because I'm only measuring at 5w2d which is about 1.5 weeks less than what I should be based on my LMP. Anyone have experience with this? Think the baby is okay? Or is it likely the baby has stopped growing?