There are lots of things you can bring that would taste just fine in your "nibbling diet". In fact there are a number of people who might envy you for not having to sit down to a full meal of meat, potatoes, veggie, desert (repeat for 2nds).
Humus and veggies, mini chicken wraps (using low-carb tortillas), almonds, peanut butter and celery or apples, low fat cheese sticks, even baked pita chips and salsa would be better than a steady diet of pizza - no matter how thin the crust is. And of course you can always bring a salad. I personally do not like my salads ice cold, but if you get a little mini cooler/lunch box you can keep it nice and chilly.
Exercise is definitely the second major component. You might think about upping your workouts to more like an hour, if 45 minutes is pretty easy. Can you go for a quick walk on your breaks rather than snacking on pizza? Just to give yourself a break from the smells and the indoors?
Just a few thoughts. As you noted in your 1st post - this is a lifestyle change, not a quicky fix.