Help about ultrasound ?

Yesterday I went for an ultrasound 5 weeks 4 days no gestational sac 🥺 I’ve had two miscarriages one successful pregnancy I have a son I really haven’t been experiencing pain no bleeding my endometrial lining measures 16.2 mm I’m so scared the dr told me don’t stress about it because my hcg level is only 595 and sometimes it takes for hcg to be in 1500-2000 range for a visible sac and I have a (38 day cycle ) my past period was nov 22 ......is there anyone that went thru this and had a successful pregnancy I’m so scared to go thru this again