Need some help..

I (O-) previously had a miscarriage in mid september , for the Rhogam shot right after. and found out I was pregnant again (around 4 weeks) on December 5th. My hcg level went from 300 from first blood work test to over 900 on the second 48 Hours later. I’m having mild cramping here and there and boobs are starting to get sore... but other than that , I don’t feel any different.. should I be worried ?? My first ultrasound is on December 19th, which is hopefully when I get to see something / or a heartbeat at least. I’m NOT bleeding. Jus need some advice. 😩😩😩