Ultrasound at 4 weeks????

Hey everyone. My doctor called me in or a 5 week ultrasound and the ultrasound came back showing nothing. I’m really only 4 weeks 6 days today but the doctor told me they should be able to see something. When the doctor notified me that they couldn’t see anything I immediately began to panic. I went home and took another pregnancy test cause I thought maybe I lost the baby. The test came back with two solid lines in less than a minute. Anyone ever have this happen to them?