That sounds normal to me. When I turned 20 weeks I'd feel movement then would go days with no movement at all. The baby is still small and still has lots of space to move around freely. If it were me, I wouldn't worry, but everyone is different.
You should probably contact ur doctor and let them know. On the packet my doctor gave me, it says to call him ASAP if there is a big decrease in fetal movement.
The normal count & my nurse always tells me to count 10 movement in an hour. U should contact ur OB if less...it's. Better to safe than sorry.