Had my first u/s at 6+1 weeks today but only yolk sac

I'm reading that this is pretty normal and my doctor also said it's still a little early to see anything but that the yolk sac is a great sign that everything is progressing well. Yet I still cant help but worry :( I really hope everything is ok. trying to stay positive. I was so looking forward to seeing the babys heartbeat and felt somewhat crushed after we left the appointment. We go back in 2 weeks and i feel like its going to be the longest 2 weeks of my life. Anyone else experience this at their first appointment?