Baby measuring small


Please tell me your stories (good, bad or ugly) about if you have ever measured weeks behind. I went in today (always had regular periods) at 7 weeks 4 days. Baby is measuring 5 weeks 5 days with a heartbeat of 110. My doctor is amazing and said she was on the fence if it was viable or not (I had a confirmed test and blood work done at 3 weeks 5 days) 4th pregnancy and I’m freaking out. Any advice?!?