Need some reassurance please

Me

I have a beautiful healthy 18 month old daughter, and suffered a mc 04/2017. I'm currently pregnant and 5+6 according to my LMP. My doctor is checking hcg and this is where I'm at:

09/05: hcg 3431 (5+3)

09/07: hcg 5839 (5+5)

Have to go back Tuesday, which would be 6+3 to have the levels rechecked. I know hcg should double every 48-72 hours, so this could still be normal but I'm freaking out.