HELP: Gestational sac but no baby

I went to the Dr yesterday and came out being told there’s only a gestational sac at this time which means only two things it’s too early or it’s a blighted ovum. The dr thought I was 6-7 weeks this week but we’re not really sure because of the irregularities in my cycle. He said if I was 5 weeks it would be normal. My sac measured 13.2 mm he said he didn’t use that size to date pregnancy, however when I looked it up it said that size was for 5 weeks 6 days. Any experience in this area? Stories welcomed!