This is my usual diet and it really hasn't changed that much.
Breakie: Rice bubbles with warm skim milk and a bit of sugar (I am struggling to loose the sugar).
Morning Tea: Nothing or some McDonalds cookies (my craving I am afraid) and a skim hot chockie.
Lunch: Vegimite s'wich or salad s'wich or bread and cupa soup (not usually that hungry at lunch).
Afternon tea: Muslie bar or snack size chockie (sometimes both).
Dinner: stir fry or chicken and salad or vegies and steak or tuna rissols and veggies (TA chinese once a week, I have the braised chicken and vegies in a tub with boiled rice). Its my treat.

I am only a shorty too. I am 5f1 and although I weighed 58kg when confirming pregnancy at 4 weeks, I am 11 weeks and was weighed last week at 57kg, but I have not really been sick and I have still been exercising at least twice a week at the gym. I think its just because I really dont eat big meals and I mainly pick all day. I can happy just having bread for lunch most of the time. But I go for the Bakers Delight Low GI bread its great.