Hi,
The spotting could be an implantation bleed. If they didnt do an internal ultrasound they probably wouldnt pick anything up, so dont be too stressed. I had a scan to date my middle son and they had to do an internal as the normal one wouldn't pick up anything, I was just five weeks and they told me I was lucky as often the internal had difficulty picking up anything so early on as well. Hang in there, You'll be fine.