Baby movement

So I'm currently 18 weeks pregnant and for the past week I've started feeling baby moving, the best way I can describe it is, it's like a little gold fish swimming around in my uterus but the thing is whenever I tell my OH and he goes to touch it he can't feel it and tbh neither can I. Like I can feel it internally but putting my hand on my stomach where I actually feel it moving I can't feel it at all which is really weird. Does anyone have any idea why? Is it still too small to feel it externally? This is my second pregnancy so I wasn't aware of any of this so early on, I just remember it was around 20+ weeks when I started to feel my son kicking externally with my hand and so did my OH. Is anyone else around 18 weeks pregnant and can actually feel the baby moving externally??