Empty Sac

I went to the ER on Jan. 1st due to bleeding and cramping, they did an ultrasound said it was too early to see anything but they seen the sac. Do blood work 2 days later it goes up, then more blood works 3 days later and it went up more. Go to my dating ultrasound today and they still didn't see anything but the sac. On jan. 1st the ultrasound said I was 5 weeks and 1 day so I would be 7 weeks today. This is my 2nd pregnancy, my 1st one went great, nothing wrong. Has this happened to anyone else? What was it called? And is there any specific that causes this? What can I do to get it through my head that there isn't a baby and one might not form? I'm having all the pregnancy symptoms, just hurts to know that its happening. I feel like I failed. 😭😭