Ultrasound scan but only water sac was seen

Hi mummies! I went for my 1st gynae appointment and also did my 1st untrasound scan today. I found out i was pregnant on 7/2/21 when i missed my period (regular period) and did 4 urine tests and even went to the GP to confirm my pregnancy. Did some EDD calculations myself and if everything's according to plan, my baby would have been 7 weeks and 5 days old today. However when i did my scan today, the doctor only found a water bag sac with almost nothing in it. I'm so shocked and sadden by this news and almost burst out crying.. But doctor reassured that this is normal as my period cycle is between 35-41 days average so might take some time for my baby to be visible and grow. Worst case scenario, there will be a 15%-20% chance of miscarriage if by the next scan there is still nothing. I'm so scared and worried.. Is there anyone out there who faces the same/similar situation as me? Please advice. Thank you! #advicepls