18 w no more baby movement

I'm 18 weeks 4 days. Around 14 weeks until 16 weeks I was feeling little twitches all the time. Now I feel absolutely nothing. I'm pretty scared. It's been probably two weeks since I've felt anything. I went in to the doc last Friday (a week and a day ago). Doc found babies heart beat and everything. I have an ultrasound in 6 days. I'm terrified the ultrasound tech is going to tell me my baby has stopped growing and is no longer alive :( any other moms ever had baby stop being active after a lot of activity before 20 weeks and everything is fine? Will my baby ever move again for me?