HCG Levels Normal?

Courtney
Hello! 
This is the first time I've taken any lab work for a pregnancy. My levels last Friday were 42. On Monday they were 184. The nurse said they are increasing like they are supposed to, but she wanted me to come in tomorrow to do Bloodwork again. I asked if this was a cause for concern, and she said it's just because it's too early to do an ultrasound. I'm just so worried from my mmc back in October. I am roughly around 5w 2d. I am just looking for some reassurance. I'm trying not to obsess about these numbers.