WELCOME TO YT!!! Have you gotten your little guy checked out by the vet? That sounds awfully small for 19 weeks. My little girl is tiny, weighing at almost 2lbs at 17 weeks but she is about 6 inches tall, but 4 seems awfully small. As long as he's healthy though. I couldn't tell you big he would get because they can go through a sudden growth spurt. Do you have pictures of your baby??
