Placenta positioning makes a huge difference. Both my boys placenta's were anterior and didn't feel any movement with DS1 till 20+ weeks and DS2 was around 19ish weeks as well. This one i know the placenta is prosterior and at the bottom also and the movements started at 16 weeks and have been alot stronger.

Just chat to the middie and they might even pop the doppler on there for you for a bit of extra reasssurance.