6 week Ultrasound and nothing there

Went in today for my first prenatal appointment at 6 weeks. Had a transvaginal ultrasound that showed nothing, not even a gestational sac. Doctor said my dates may be off and I'm still too early to see anything or it may be an early ectopic. I'm having no cramping or spotting at all. And the pregnancy test I took this morning was same or darker than control line. They drew blood to test levels and I'm scheduled for another ultrasound on Tuesday. Has anyone else had this happen and had a positive outcome?

(Attached today's test - results within 3 minutes)