Feeling baby kick 👣

This is my second pregnancy. With my first I remember feeling my baby move at 16 weeks and it only got stronger. I’m almost 20 weeks and I barely feel my baby move. When I do it’s just flutters although I have felt some stronger kicks here and there. It kind of worries me. At my 13 week appointment we couldn’t find his heartbeat on the Doppler machine. I was sent in to get an ultrasound and we found it but I’m wondering if he is behind my placenta and if that’s why I can’t really feel him kick and if that’s why we couldn’t find the heartbeat when he was so little. Does anyone have experience with this?