Ultrasound issue!

Victoria
Had an ultrasound yesterday at 7w3d.  The dr automatically said when he did the transvag that I'm only 6 weeks.  We saw a little bean with a heartbeat but it was only ABT 100bpm.  So now I have to go back Monday.  He wants to see if I'm just early or if fetal heart development isn't developing correctly.  Freaking out.  Anyone has this happen?