It can be due to the placenta position, if anterior it can act as a cushion and it's harder to fell kicks and movement. I would suggest to speak to your midwife but chance are they would say it's still early. I'm 17w and what I feel is really subtle, like flutters and tiny kicks.
Every pregnancy is different. It also depends where the placenta is. As if it's anterior then you most likely won't feel baby until 20+ weeks xx
As has been said above, pregnancies are all different. Placental position may well be a factor. x
I imagine every pregnancy is different but I imagine it must be worrying for you! You could try contacting your midwife, I assume you've already had your 16 week appt?