Yolk Sac; no fetal pole


Hello! Just to brief, I have 2 children already and I had an ectopic, losing my Fallopian tube March 2017. I’ve been keeping up with my period and some what my ovulation on Glow for a few months since I’ve become a bit irregular since then. After only 3 days of missing my cycle, I took a test just to ease my mind and it was POSITIVE but pretty dark. Based on my ovulation dates I figured I was only 3-4 weeks pregnant but pushed for an ultrasound to make sure it wasn’t ectopic. The ultrasound tech seen a yolk sac but no baby yet. Has anyone experienced this before? They drew blood today, will draw again on Thursday and I have another ultrasound in a week.