Nothing on the ultrasound at 5 weeks

We found out we were pregnant 2 weeks ago and were confirmed in clinic a week ago. At that time I had an ultrasound to determine if the baby was in the right spot, since a year ago we had an ectopic pregnancy. Today the doctor phoned me back with the results and she said there may be complications with the pregnancy since they couldn't see anything in the uterus. I am scheduled for another ultrasound and blood work tomorrow morning to see what my levels are. 
I guess my question is has anyone else had this problem? Is there a chance that 5 weeks was to early to see anything at all and that tomorrow at 6 weeks we may see something different? My biggest fear is gong through an ectopic pregnancy again...