Haha totally normal laa, at 16 weeks memang macam tu! A few of us felt the same thing, one friend said it's like "butterflies with gas" Baby movements at this stage are super subtle so you won't be sure sampai nanti it gets stronger, but bila you lie down memang easier to notice sebab gravity and all. Jangan confuse yourself, it could genuinely be baby, bisa juga just your digestion being dramatic, both are happening in your uterus area so mana tahu kan!