It can also depend on what your weight is. If you were thinner with your last pregnancy you may have felt it sooner, where as if you are heavier this time it may be later. It's not cause for concern unless you don't start feeling constitant movement by 24 weeks. I am on my 8th pregnancy (4 kids 3 angels in heaven). Some babies move more than others. It can also depend on the position of your uterus as well. If your concerned it's never a bad idea to bring it up to your doctor.
Mine started to move at 20weeks - 1 day. Until then I had felt absolutely nothing.
I know it is hard not to worry but try to relax. It is not uncommon at all. The norm for fetal movement is anywhere between 16-24 wks, so you are all good! I bet in no time your baby will be bouncing off the walls!!!!
When is your next ob appt??? Hearing the HB on the doppler always made me feel better!!!!
from the sounds of it your baby is fine. You might start to notice that the baby will move alot more at about 22 weeks as that what happens sometimes. No need to worry, your baby is fine :) x