6w4d Abdominal US Shows Empty Sac

I went to a “Sneak a Peek” location and was told they can see the gestational sac but nothing else. I’ve been experiencing brown discharge and pain on my right side, which my doctor didn’t seem worried about when I reached out to them. I have a vaginal US with my doctor tomorrow. I’m wondering if anyone else had a similar experience with an abdominal US?