Measuring behind…

Just got back from the ER bc I’ve been having some pretty intense cramping. I was under the impression that I was 6 weeks 2 days today but the ultrasound only showed the sack and a white spec that will hopefully turn into my baby. No fetal pole. They said I’m measuring approximately 4-5 weeks. My beta levels were 6,896 and I go back in 3 days to make sure they double. Anyone else experience anything like this and have a healthy pregnancy? I’m trying not to stress but of course that’s easier said than done!