I second that. I'm sure all is fine but it's easy for mamas to worry. At my 20 wk u/s she was moving around a lot and I only felt some of them. Even now at almost 22 wks I don't feel her very often unless I'm sitting up - like on the couch or in a chair. It must be something with how she is positioned most of the time. If I'm standing I hardly ever feel her.
I hope you have a great appt!