Emily,
Do not sweat it. The numbers could be off or your muscle mass may not be as much as you would like. Build some weights into your routine, if you are concerned. I used to be your weight (long time ago) and now I am heavier (size 6) but a lot stronger than I was when I weighed less. I have no idea if there is any correlation at all. I am 15 years older and 3 kids later, my body shape has completely changed, so I imagine there are numerous factors involved.
Basically, I think I managed to say nothing.
Jennifer
“Live as if you were to die tomorrow. Learn as if you were to live forever.”
-Mahatma Gandhi
"We are what we repeatedly do. Excellence, therefore, is not an act but a habit."
-Aristotle