I have just been worrying about this lately too! Last week at my doctors office, my doc told me that I shouldn't be worried about feeling the baby on a regular basis until 28 wks, which helped me feel some better. But it is still a nerve wracking when something seems different. I agree with what the other mom's said about the position of the baby. Last night I was doing everything to try to get my little baby to move, so I could feel better, and I got nothing until I laid down to go to sleep... then she started dancing

Hopefully you will get some reassuring movement soon or call your doc if it will help you feel better.