Wrap dresses!! You can wear them to work and the ruching covers up your little belly.
Summer is really the perfect time to be in your first/early second trimester because of the flowy tops out there. Check out Nordstrom and the Limited. And yes, the bella band is your friend.
I had to do this in the winter, when I typically wear pencil skirts and slim sweaters - fortunately, it was also around the holidays, so maybe people thought I was just overindulging at Thanksgiving/Christmas?