5+5 ultrasound, no fetal pole

I have history of two pregnancy losses so after my HCG doubled last week from 365 to 856, my ob scheduled me for an early scan which was this morning. It was a transvaginal US. She said there was a gestational sac and a yolk sac but no fetal pole. She's hesitant because she said if going by my numbers 8 days ago I should well be over 12,000 HCG and by now there should be a fetal pole or a slight heart beat. She's ordered a couple more HCG betas to be done and then she'll set up another appt in a week or two.

I'm really really trying my best to stay positive. Please share your experiences. Picture of ultrasound below: