Baby movement

I have a posterior placenta and am 16 weeks. Doctors keep saying I’ll feel movements early. I keep reading baby movement is more like flutters or bubbles but occasionally I feel a pretty centralized tightening in places. Could this still be the baby moving or is this Braxton hix? It doesn’t go across my whole uterus when it happens. I am a thin person so wondering if that is why baby movement might feel different to me too. Or maybe it’s just my uterus stretching. It’s confusing!