YYZ,
Just like what the other moms said, there are many reasons of losing weight. If it's not a lot and it's not a continuous consequence, it may not a real problem. You can consult a doctor if you really concern or it bother you.
One of the reasons that I can think of - may be your baby Shing Hay has been more active these days. Baby eats more but also his body needs more to cover the loss of energy from his daily activities. My kids also lost weight some time when they are sick, sleep less or play a lot without enough resting. So, take it easy and keep your good work. Wait and see and talk to a doctor if the problem gets worse.
花旗太太生活在花旗國,留意時差,你問我未必即時答到。