Baby Did Not Show On Ultrasound

Hi guys I’m hoping someone can give me their opinion on here.. 2 weeks ago I went to an ultrasound center to confirm my pregnancy, I decided to do this because I just got a new job and need to wait for my insurance to kick in so this option was cheaper as to oppose to going to my doctor and paying a $300 bill. When I got there and the lady was checking she went on mentioning that it’s confirmed 100% I am pregnant she even measured a tiny little thing, stated the sac look gorgeous. However asked me to come back for a free visit to hear the heart beat after 2 weeks, that was yesterday. When my is husband and I went there was another lady this time and when she checked she couldn’t see anything, I even drank more water and when she checked again she could not see anything. I also had a miscarriage on September 7th so I’m super worried. Can you guys please tell me if this has ever happened to you.. I now need to schedule an appointment with my doctor.