Haha sis, at 19 weeks tu mmg susah nak tau lagi especially kalau first pregnancy! That bubble-like sensation you're feeling could very well be baby movements, a few of my mum friends said dekat 4-5 months they felt macam "butterflies" or "gas" jugak, and they weren't sure if it was the baby or angin perut je. The thing is, first-time mums usually feel baby movements slightly later compared to those who've been pregnant before, so jangan worry if you're not 100% sure yet, masa masuk 20-something weeks nanti you'll start feeling yang lagi obvious, macam actual little kicks and rolls yang you can't mistake for anything else! For now, just observe kalau rasa apa at certain times of the day, pastu nanti when it becomes clearer you'll be like "OH THAT'S THE BABY!"