I had an ultrasound this morning and all is well. The yolk sac measured at 3 mm. It appears that the ultrasound nurse misread or mis-measured the yolk sac last week, so it was probably never enlarged in the first place. The baby is looking great, heartbeat is great and there are no concerns. I'm very relieved but also a little irritated at the nurse's error. (My pregnancy nurse shares that sentiment) I'll have my first OB appt tomorrow morning and will also go for that blood DNA test. I was going to cancel it but I figure I may as well get it for my peace of mind.