My baby is 3 weeks old.; I can see all new mothers r worried about bm, but I was not.; But now I m little worried.; How can we understand whether my lol gets enough milk? Whether her stomach is full or not?

My breast is not at all leaking,; but whet n I check even after feeding milk is there.; I m feeding her till she sleeps and; unlatches herself.; I thought that she sleeps bcz her stmch is full.; Day time it's fine.; But in night every 1.5 hrs she gets up nd demands 4 milk. And if I m late 2 mins for feeding she behaves asif she was not feed for hrs.; Does it mean that she is hungry nd her stmch is not full? Plzzz help