HCG not doubling?

This is my second pregnancy and if it's going to be anything like my first one then I'm in for a ride. I went in on Friday and my hcg was 235. On Sunday it was 437. It almost doubled but not all the way. My progesterone level was 20.2 so they said that was fine. I've also had cramping and some light brown spotting but that's been going on since before I found out I was pregnant. Any advice would be great. Thanks 😊