Miscarriage, maybe

I went to my first pregnancy appointment at what was supposed to be 8 weeks. They said it looks more like 6 weeks, and the yolk sac is larger than it should be, and that the heart rate is slow--only 94 BPM. They changed my due date to reflect 6 weeks pregnancy and said call if this or that. The midwife sounded like she expects me to miscarry. This was about a week ago. Nothing has happened.

This is my first pregnancy. I don't know how to feel, and I'm just waiting for something to happen. I haven't had many symptoms, mostly just sore breasts.

I guess I don't really have a question. Just looking for some reassurance, maybe. Anyone had a similar experience?