Yup! My first time also cannot see baby, not even the sac. Then doctor scheduled two weeks later and managed to see the sac and baby heartbeat despite it being a small dot.
By right I should be at week 7 but then doctor says it's only at week 6. Still very small.
So maybe yours also because baby is still too small to be seen! Don't be despair and think negatively. Think positive thoughts so baby will be strong with you okay! Fighting!
Thank you for sharing, I'm really feeling much better, and positive