When Will You Appear?

Hi! How many weeks will the baby appear on the ultrasound? As per this application, I am currently 6 weeks and 6 days pregnant and I took a Serum test as well and it is positive. I took a TransV yesterday but my uterus is clear and there is no trace of pregnancy yet. I have PCOS before. Maybe it is too early for the baby to be detected on the ultrasound? Is it possible that I conceived later than the computed dates?