mostly genetics, i am sure.
I definately seem to eat less per sitting than i used to... baby is squashing my tummy i am sure... but thing is i will soon be hungry again and make up for the loss...
Before i got pregnant i used to eat only supper... which really annoyed my GP but thats another story
Now i eat at ten and again at twelve and then supper at 5ish... not to mention snacking in between on whatever happens to cross my path...
I read that you only need one extra small snack a day to sustain the pregnancy, anything after that is extra... but if i were were you i'd say trust your instincts your body will let you know if you need the food or not... eat if you are hungry. And if you feel like a glass of milk before bed have it (i see at some point or another most of us have developed the habbit)

DH and i discovered at the grocery store that they sell 1 litre super M in strawberry and chocolate... so every few weeks we get one of each, he has a glass of chocolate and i have the strawberry every night as desert...