Sayang, weight loss yang tiba-tiba during pregnancy memang perlu check dengan doctor, especially at 19 weeks! Jangan delay, boleh go see your OB atau terus ke clinic untuk peace of mind. A few of my mum friends experienced something similar and turned out OK, but setiap pregnancy berbeza, so it's always better to get it checked out properly. Could be normal (hormones, morning sickness still lingering), tapi doctor kena tahu. Jangan worry dulu, just go get it sorted out, eh!