HCG.. can someone please calm my nerves?!

I got my first faint positive 10/21 and I think I ovulated on around 10/8. My first HCG on 10/25 was 99, two days later it was 226. My doctor said they're doubling so they aren't going to retest for 2 weeks, but those seem pretty low to me. It's making my very worried that I am going to miscarry. Other than breast tenderness and fatigue I really don't have have any pregnancy symptoms.