Trying to stay positive

After measuring only 6mm and not seeing a heartbeat at my 8wk ultrasound, I'm nervous how this will play out. The doctor said she can't rule it as a miscarriage or not without the lab work to back it up. Did first round of blood work yesterday and go back tomorrow morning for round 2. Then I get another ultrasound done Friday the 17th. I hope the baby is just off to a slow start and will catch up quickly. This is my first time ttc. I've heard it can go either way. .. Any other ladies have experience with this?