Could this be a healthy sac but out of the ultrasounds range/focus and/or is it an ectopic pregnancy?

I got my 6w3d ultrasound and says that there may be a POSSIBLE gestational sac but it's very small, oddly shaped and cannot make out if there is anything inside of it. They believe it is an ectopic pregnancy because my HCG levels plateaued last week. At 15dpo 347, 17dpo 1250, 19dpo 3864, 24dpo 5249, 26dpo 5194, 27dpo 5671, 30dpo 11466. My thought for the plateau would be vanishing twin be she totally denies this. But now the ultrasound is inconclusive, so I would like another opinion.