Empty sac advice

Hi all! I’m on my second pregnancy now. The first one was about a year ago and was deemed non-viable. I formed a pregnancy sac, but nothing ever showed and had a C&D at about 11 weeks.

According to my period (sometimes erratic) I should be 6w5d. I went to the doctor and my pregnancy sac measured 5d5w, and is empty.

I’m going to go for HCG tests next week and going back for another ultrasound in 2 weeks.

My first pregnancy test (about a week ago) showed a pretty faint positive and the one today showed a bold positive line.

Can anyone shed some light on the empty sac? The next two weeks are going to be the longest, and just trying to stay sane until the next ultrasound.